cmake-gui: Use the QStandardItemModel workaround until 5.1.0.

If there is a Qt 5.0.3 release, it may or may not contain the patch
that fixes this issue.

 http://thread.gmane.org/gmane.comp.lib.qt.releasing/882

Just use the workaround until 5.1.0 which certainly will contain the
fix. Don't use the workaround before Qt 5.0.0.

Source/QtDialog/QCMakeCacheView.cxx

@@ -491,7 +491,7 @@ QCMakePropertyList QCMakeCacheModel::properties() const
 
       // go to the next in the tree
       while(!idxs.isEmpty() && (
-#if QT_VERSION < QT_VERSION_CHECK(5, 0, 3)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0) && QT_VERSION < QT_VERSION_CHECK(5, 1, 0)
         (idxs.last().row()+1) >= rowCount(idxs.last().parent()) ||
 #endif
         !idxs.last().sibling(idxs.last().row()+1, 0).isValid()))