Recognize gccgo error messages:

func4.go:8:11: error: invalid operand for unary '&'
func4.go:9:8: error: invalid left hand side of assignment

R=rsc
DELTA=2  (0 added, 0 deleted, 2 changed)
OCL=24294
CL=24603

test/func4.go

@@ -9,6 +9,6 @@ package main
 var notmain func()
 
 func main() {
-	var x = &main;		// ERROR "address of function"
-	main = notmain;	// ERROR "assign to function"
+	var x = &main;		// ERROR "address of function|invalid"
+	main = notmain;	// ERROR "assign to function|invalid"
 }