c++: Fux strncmp last argument in dump_decl_name [PR93641]

I'm not aware of symbols starting with _ZG that don't start with _ZGR
prefix, but perhaps in the future there might be some.

2020-02-10  Jakub Jelinek  <jakub@redhat.com>

	PR other/93641
	* error.c (dump_decl_name): Fix up last argument to strncmp.

gcc/cp/ChangeLog

+2020-02-10  Jakub Jelinek  <jakub@redhat.com>
+
+	PR other/93641
+	* error.c (dump_decl_name): Fix up last argument to strncmp.
+
 2020-02-10  Jason Merrill  <jason@redhat.com>
 
 	PR c++/93618

gcc/cp/error.c

@@ -1098,7 +1098,7 @@ dump_decl_name (cxx_pretty_printer *pp, tree t, int flags)
     }
 
   const char *str = IDENTIFIER_POINTER (t);
-  if (!strncmp (str, "_ZGR", 3))
+  if (!strncmp (str, "_ZGR", 4))
     {
       pp_cxx_ws_string (pp, "<temporary>");
       return;