compiler: fix quoting in error message

Reviewed-on: https://go-review.googlesource.com/23966

From-SVN: r237286

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-a87af72757d9a2e4479062a459a41d4540398005
+054ff1ece3dd5888a445efeaf3ae197b16d4186f
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.cc

@@ -11463,7 +11463,7 @@ Selector_expression::lower_method_expression(Gogo* gogo)
 
   if (method != NULL && !is_pointer && !method->is_value_method())
     {
-      error_at(location, "method requires pointer (use %<(*%s).%s)%>",
+      error_at(location, "method requires pointer (use %<(*%s).%s%>)",
 	       nt->message_name().c_str(),
 	       Gogo::message_name(name).c_str());
       return Expression::make_error(location);