class.c (add_method): Do compare 'this' quals when trying to match a used function.

        * class.c (add_method): Do compare 'this' quals when trying to match a
        used function.  Don't defer to another used function.

From-SVN: r48158

gcc/testsuite/g++.dg/lookup/using.C

@@ -17,7 +17,7 @@ struct Derived : Base {
 int main()
 {
   Derived d;
-  X x = d.f();                  // { dg-bogus "Y" "" { xfail *-*-* } }
+  X x = d.f();                  // { dg-bogus "Y" "" }
 }