Small addition to previous optimization of memequal as discussed here:…

Small addition to previous optimization of memequal as discussed here: http://groups.google.com/group/golang-nuts/browse_thread/thread/f591ba36d83723c0/9aba02d344045f38

R=golang-dev, r, r2
CC=golang-dev
https://golang.org/cl/2880041

src/pkg/runtime/runtime.c

@@ -320,6 +320,8 @@ memequal(uint32 s, void *a, void *b)
 {
 	byte *ba, *bb, *aend;
 
+	if(a == b)
+	  return 1;
 	ba = a;
 	bb = b;
 	aend = ba+s;