test: Recognize gccgo error messages.

bug299.go:16:2: error: expected field name
bug299.go:17:2: error: expected field name
bug299.go:18:3: error: expected field name
bug299.go:25:9: error: expected receiver name or type
bug299.go:26:10: error: expected receiver name or type
bug299.go:27:9: error: expected receiver name or type

R=rsc
CC=golang-dev
https://golang.org/cl/2150044

test/fixedbugs/bug299.go

@@ -22,6 +22,6 @@ type T struct {
 func (p T) m() {}
 
 // not legal according to spec
-func (p (T)) f() {}   // ERROR "parenthesize"
-func (p *(T)) g() {}  // ERROR "parenthesize"
-func (p (*T)) h() {}  // ERROR "parenthesize"
+func (p (T)) f() {}   // ERROR "parenthesize|expected"
+func (p *(T)) g() {}  // ERROR "parenthesize|expected"
+func (p (*T)) h() {}  // ERROR "parenthesize|expected"