Rename Qt-specific GetEventType() to start with "Qt" prefix

This avoids conflicts with another method with the same name defined in
generic wxGenericFileDirButton, which must neither override nor hide
this method of wxButton.

include/wx/qt/anybutton.h

@@ -29,7 +29,7 @@ public:
 
     // implementation only
     void QtUpdateState();
-    virtual int GetEventType() const = 0;
+    virtual int QtGetEventType() const = 0;
 
 protected:
     virtual wxBitmap DoGetBitmap(State state) const wxOVERRIDE;