Recognize gccgo error message.

const2.go:7:9: error: expected '='

Uses '.' to recognize the quotation marks, as the actual
characters printed depend on the user's locale.

R=rsc
DELTA=1  (0 added, 0 deleted, 1 changed)
OCL=26360
CL=26373

test/const2.go

@@ -8,5 +8,5 @@ package main
 
 const (
 	A int = 1;
-	B byte;	// ERROR "type without expr"
+	B byte;	// ERROR "type without expr|expected .=."
 )