Add appengine and noasm build tags.
The general suggestion to use a noasm tag is by Klaus Post at
https://groups.google.com/d/msg/golang-dev/CeKX81B3WdQ/2mq-eY0VAgAJ
diff --git a/decode_amd64.go b/decode_amd64.go
index cbcd464..fcd192b 100644
--- a/decode_amd64.go
+++ b/decode_amd64.go
@@ -2,7 +2,9 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+// +build !appengine
// +build gc
+// +build !noasm
package snappy
diff --git a/decode_amd64.s b/decode_amd64.s
index 099d096..030cafc 100644
--- a/decode_amd64.s
+++ b/decode_amd64.s
@@ -2,7 +2,9 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+// +build !appengine
// +build gc
+// +build !noasm
#include "textflag.h"
diff --git a/decode_other.go b/decode_other.go
index b557136..f305b6f 100644
--- a/decode_other.go
+++ b/decode_other.go
@@ -2,7 +2,7 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
-// +build !amd64 !gc
+// +build !amd64 appengine !gc noasm
package snappy
