Add an mx.Handle.Signal method

Change-Id: I816ee34130034791d06570f8e3e9aa88bd836700
diff --git a/src/syscall/mx/handle.go b/src/syscall/mx/handle.go
index d0da5c7..ef86834 100644
--- a/src/syscall/mx/handle.go
+++ b/src/syscall/mx/handle.go
@@ -110,6 +110,13 @@
 	return observed, nil
 }
 
+func (h Handle) Signal(clearMask, setMask Signals) error {
+	if status := Sys_object_signal(h, uint32(clearMask), uint32(setMask)); status != ErrOk {
+		return Error{Status: status, Text: "mx.Handle.Signal"}
+	}
+	return nil
+}
+
 func (h Handle) SignalPeer(clearMask, setMask Signals) error {
 	if status := Sys_object_signal_peer(h, uint32(clearMask), uint32(setMask)); status != ErrOk {
 		return Error{Status: status, Text: "mx.Handle.SignalPeer"}