protoc-gen-go: regenerate golden tests (#540)

New tests weren't updated for renamed Marshal/Unmarshal methods.
diff --git a/protoc-gen-go/testdata/imports/fmt/m.pb.go b/protoc-gen-go/testdata/imports/fmt/m.pb.go
index 6892d6e..359ed1b 100644
--- a/protoc-gen-go/testdata/imports/fmt/m.pb.go
+++ b/protoc-gen-go/testdata/imports/fmt/m.pb.go
@@ -28,10 +28,10 @@
 func (m *M) String() string            { return proto.CompactTextString(m) }
 func (*M) ProtoMessage()               {}
 func (*M) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
-func (m *M) Unmarshal(b []byte) error {
+func (m *M) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M.Unmarshal(m, b)
 }
-func (m *M) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *M) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_M.Marshal(b, m, deterministic)
 }
 func (dst *M) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go b/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go
index d04309c..158b8f3 100644
--- a/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go
+++ b/protoc-gen-go/testdata/imports/test_a_1/m1.pb.go
@@ -28,10 +28,10 @@
 func (m *M1) String() string            { return proto.CompactTextString(m) }
 func (*M1) ProtoMessage()               {}
 func (*M1) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
-func (m *M1) Unmarshal(b []byte) error {
+func (m *M1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M1.Unmarshal(m, b)
 }
-func (m *M1) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *M1) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_M1.Marshal(b, m, deterministic)
 }
 func (dst *M1) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go b/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go
index 06a2be5..40050fd 100644
--- a/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go
+++ b/protoc-gen-go/testdata/imports/test_a_1/m2.pb.go
@@ -22,10 +22,10 @@
 func (m *M2) String() string            { return proto.CompactTextString(m) }
 func (*M2) ProtoMessage()               {}
 func (*M2) Descriptor() ([]byte, []int) { return fileDescriptor1, []int{0} }
-func (m *M2) Unmarshal(b []byte) error {
+func (m *M2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M2.Unmarshal(m, b)
 }
-func (m *M2) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *M2) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_M2.Marshal(b, m, deterministic)
 }
 func (dst *M2) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go b/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go
index 88e6bf2..40830a2 100644
--- a/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go
+++ b/protoc-gen-go/testdata/imports/test_a_2/m3.pb.go
@@ -28,10 +28,10 @@
 func (m *M3) String() string            { return proto.CompactTextString(m) }
 func (*M3) ProtoMessage()               {}
 func (*M3) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
-func (m *M3) Unmarshal(b []byte) error {
+func (m *M3) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M3.Unmarshal(m, b)
 }
-func (m *M3) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *M3) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_M3.Marshal(b, m, deterministic)
 }
 func (dst *M3) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go b/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go
index 95720d8..5d4040c 100644
--- a/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go
+++ b/protoc-gen-go/testdata/imports/test_a_2/m4.pb.go
@@ -22,10 +22,10 @@
 func (m *M4) String() string            { return proto.CompactTextString(m) }
 func (*M4) ProtoMessage()               {}
 func (*M4) Descriptor() ([]byte, []int) { return fileDescriptor1, []int{0} }
-func (m *M4) Unmarshal(b []byte) error {
+func (m *M4) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M4.Unmarshal(m, b)
 }
-func (m *M4) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *M4) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_M4.Marshal(b, m, deterministic)
 }
 func (dst *M4) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go b/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go
index 3a608c2..be9ac92 100644
--- a/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go
+++ b/protoc-gen-go/testdata/imports/test_b_1/m1.pb.go
@@ -28,10 +28,10 @@
 func (m *M1) String() string            { return proto.CompactTextString(m) }
 func (*M1) ProtoMessage()               {}
 func (*M1) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
-func (m *M1) Unmarshal(b []byte) error {
+func (m *M1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M1.Unmarshal(m, b)
 }
-func (m *M1) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *M1) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_M1.Marshal(b, m, deterministic)
 }
 func (dst *M1) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go b/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go
index 56e9c5d..5022a27 100644
--- a/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go
+++ b/protoc-gen-go/testdata/imports/test_b_1/m2.pb.go
@@ -22,10 +22,10 @@
 func (m *M2) String() string            { return proto.CompactTextString(m) }
 func (*M2) ProtoMessage()               {}
 func (*M2) Descriptor() ([]byte, []int) { return fileDescriptor1, []int{0} }
-func (m *M2) Unmarshal(b []byte) error {
+func (m *M2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_M2.Unmarshal(m, b)
 }
-func (m *M2) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *M2) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_M2.Marshal(b, m, deterministic)
 }
 func (dst *M2) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go b/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go
index b6d5abb..dd3bd1b 100644
--- a/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go
+++ b/protoc-gen-go/testdata/imports/test_import_a1m1.pb.go
@@ -30,10 +30,10 @@
 func (m *A1M1) String() string            { return proto.CompactTextString(m) }
 func (*A1M1) ProtoMessage()               {}
 func (*A1M1) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
-func (m *A1M1) Unmarshal(b []byte) error {
+func (m *A1M1) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_A1M1.Unmarshal(m, b)
 }
-func (m *A1M1) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *A1M1) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_A1M1.Marshal(b, m, deterministic)
 }
 func (dst *A1M1) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go b/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go
index abf5085..3ce4478 100644
--- a/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go
+++ b/protoc-gen-go/testdata/imports/test_import_a1m2.pb.go
@@ -24,10 +24,10 @@
 func (m *A1M2) String() string            { return proto.CompactTextString(m) }
 func (*A1M2) ProtoMessage()               {}
 func (*A1M2) Descriptor() ([]byte, []int) { return fileDescriptor1, []int{0} }
-func (m *A1M2) Unmarshal(b []byte) error {
+func (m *A1M2) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_A1M2.Unmarshal(m, b)
 }
-func (m *A1M2) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *A1M2) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_A1M2.Marshal(b, m, deterministic)
 }
 func (dst *A1M2) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_import_all.pb.go b/protoc-gen-go/testdata/imports/test_import_all.pb.go
index 08bf252..db5dc8f 100644
--- a/protoc-gen-go/testdata/imports/test_import_all.pb.go
+++ b/protoc-gen-go/testdata/imports/test_import_all.pb.go
@@ -36,10 +36,10 @@
 func (m *All) String() string            { return proto.CompactTextString(m) }
 func (*All) ProtoMessage()               {}
 func (*All) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{0} }
-func (m *All) Unmarshal(b []byte) error {
+func (m *All) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_All.Unmarshal(m, b)
 }
-func (m *All) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *All) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_All.Marshal(b, m, deterministic)
 }
 func (dst *All) XXX_Merge(src proto.Message) {
diff --git a/protoc-gen-go/testdata/imports/test_import_public.pb.go b/protoc-gen-go/testdata/imports/test_import_public.pb.go
index 8cdfdec..94458c6 100644
--- a/protoc-gen-go/testdata/imports/test_import_public.pb.go
+++ b/protoc-gen-go/testdata/imports/test_import_public.pb.go
@@ -16,12 +16,12 @@
 // M1 from public import imports/test_a_1/m1.proto
 type M1 test_a.M1
 
-func (m *M1) Reset()                     { (*test_a.M1)(m).Reset() }
-func (m *M1) String() string             { return (*test_a.M1)(m).String() }
-func (*M1) ProtoMessage()                {}
-func (m *M1) Unmarshal(buf []byte) error { return (*test_a.M1)(m).Unmarshal(buf) }
-func (m *M1) Marshal(b []byte, deterministic bool) ([]byte, error) {
-	return (*test_a.M1)(m).Marshal(b, deterministic)
+func (m *M1) Reset()                         { (*test_a.M1)(m).Reset() }
+func (m *M1) String() string                 { return (*test_a.M1)(m).String() }
+func (*M1) ProtoMessage()                    {}
+func (m *M1) XXX_Unmarshal(buf []byte) error { return (*test_a.M1)(m).XXX_Unmarshal(buf) }
+func (m *M1) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return (*test_a.M1)(m).XXX_Marshal(b, deterministic)
 }
 func (m *M1) XXX_Size() int       { return (*test_a.M1)(m).XXX_Size() }
 func (m *M1) XXX_DiscardUnknown() { (*test_a.M1)(m).XXX_DiscardUnknown() }
@@ -37,10 +37,10 @@
 func (m *Public) String() string            { return proto.CompactTextString(m) }
 func (*Public) ProtoMessage()               {}
 func (*Public) Descriptor() ([]byte, []int) { return fileDescriptor3, []int{0} }
-func (m *Public) Unmarshal(b []byte) error {
+func (m *Public) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Public.Unmarshal(m, b)
 }
-func (m *Public) Marshal(b []byte, deterministic bool) ([]byte, error) {
+func (m *Public) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
 	return xxx_messageInfo_Public.Marshal(b, m, deterministic)
 }
 func (dst *Public) XXX_Merge(src proto.Message) {