loplugin: use TypeCheck instead of getQualifiedNameAsString

since the latter is rather slow

Change-Id: Ib73cdb923585580777c2265b561c1808e93b2baa
Reviewed-on: https://gerrit.libreoffice.org/33585
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/staticmethods.cxx

@@ -46,7 +46,7 @@ bool BaseCheckNotTestFixtureSubclass(
 #endif
     )
 {
-    if (BaseDefinition->getQualifiedNameAsString().compare("CppUnit::TestFixture") == 0) {
+    if (loplugin::TypeCheck(BaseDefinition).Class("TestFixture").Namespace("CppUnit").GlobalNamespace()) {
         return false;
     }
     return true;