Tweak comments so that this test passes with gccgo.

bug126.go:7:7: error: redefinition of 'none'
bug126.go:6:7: note: previous definition of 'none' was here

R=gri
DELTA=3  (1 added, 0 deleted, 2 changed)
OCL=20563
CL=20723

test/bugs/bug126.go

@@ -6,5 +6,6 @@
 
 package main
 
-const none = 0  // same const identifier declared twice should not be accepted
-const none = 1  // ERROR "redeclared"
+// same const identifier declared twice should not be accepted
+const none = 0  // GCCGO_ERROR "previous"
+const none = 1  // ERROR "redeclared|redef"