Recognize gccgo error messages. This uses GCCGO_ERROR, which

is recognized by the gccgo testsuite but is ignored by the
errchk script used with 6g.

method1.go:7:1: error: redefinition of 'M': parameter types changed
method1.go:6:1: note: previous definition of 'M' was here
method1.go:10:1: error: redefinition of 'f': parameter types changed
method1.go:9:1: note: previous definition of 'f' was here
method1.go:13:1: error: redefinition of 'g': parameter names changed
method1.go:12:1: note: previous definition of 'g' was here

R=rsc
DELTA=5  (0 added, 0 deleted, 5 changed)
OCL=18962
CL=19058

test/method1.go

@@ -7,12 +7,12 @@
 package main
 
 type T struct { }
-func (t *T) M(int, string);
-func (t *T) M(int, float) { }   // ERROR "redeclared"
+func (t *T) M(int, string);	// GCCGO_ERROR "previous"
+func (t *T) M(int, float) { }   // ERROR "redeclared|redefinition"
 
-func f(int, string);
-func f(int, float) { }  // ERROR "redeclared"
+func f(int, string);	// GCCGO_ERROR "previous"
+func f(int, float) { }  // ERROR "redeclared|redefinition"
 
-func g(a int, b string);
+func g(a int, b string);  // GCCGO_ERROR "previous"
 func g(a int, c string);  // ERROR "names changed"