Recognize gccgo error messages.

rename1.go:10:8: error: expected type
rename1.go:11:10: error: expected function
rename1.go:13:8: error: incompatible types in binary expression

R=rsc
http://go/go-review/1015013

test/rename1.go

@@ -7,10 +7,10 @@
 package main
 
 func main() {
-	var n byte;	// ERROR "not a type"
-	var y = float(0);	// ERROR "cannot call"
+	var n byte;	// ERROR "not a type|expected type"
+	var y = float(0);	// ERROR "cannot call|expected function"
 	const (
-		a = 1+iota;	// ERROR "string"
+		a = 1+iota;	// ERROR "string|incompatible types"
 	)
 
 }