qt4: Define Q_DECL_OVERRIDE for Qt4

Signed-off-by: Tristan Matthews <le.businessman@gmail.com>

modules/gui/qt4/qt4.hpp

@@ -43,6 +43,11 @@
 #define HAS_QT47 ( QT_VERSION >= 0x040700 )
 #define HAS_QT5  ( QT_VERSION >= 0x050000 )
 
+/* Q_DECL_OVERRIDE is a Qt5 feature, add empty define to not break with Qt4 */
+#if !HAS_QT5 && !defined(Q_DECL_OVERRIDE)
+# define Q_DECL_OVERRIDE
+#endif
+
 enum {
     DialogEventTypeOffset = 0,
     IMEventTypeOffset     = 100,