test: match gccgo error messages for bug325.go.

bug325.go:13:10: error: invalid indirect of ‘unsafe.Pointer’
bug325.go:14:31: error: reference to field ‘foo’ in object which has no fields or methods

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/4313050

test/fixedbugs/bug325.go

@@ -11,5 +11,5 @@ import "unsafe"
 func main() {
 	var x unsafe.Pointer
 	println(*x) // ERROR "invalid indirect.*unsafe.Pointer"
-	var _ = (unsafe.Pointer)(nil).foo  // ERROR "no field or method foo"
+	var _ = (unsafe.Pointer)(nil).foo  // ERROR "foo"
 }