test: match gccgo error messages for syntax/chan.go.

chan.go:11:1: error: unexpected ‘}’ in channel type
chan.go:13:16: error: unexpected ‘)’ in channel type
chan.go:16:16: error: unexpected comma in channel type

R=golang-dev, rsc1
CC=golang-dev
https://golang.org/cl/4313055

test/syntax/chan.go

@@ -8,9 +8,9 @@ package main
 
 type xyz struct {
     ch chan
-} // ERROR "unexpected } in channel type"
+} // ERROR "unexpected .*}.* in channel type"
 
-func Foo(y chan) { // ERROR "unexpected \) in channel type"
+func Foo(y chan) { // ERROR "unexpected .*\).* in channel type"
 }
 
 func Bar(x chan, y int) { // ERROR "unexpected comma in channel type"