Define Q_DECL_OVERRIDE for Qt4

That macro is new in Qt5, define it as well when compiling with Qt4
so we can use it in mirall

Note: QNetworkCookieJar::deleteCookie was not existing in Qt4.

cmake/modules/QtVersionAbstraction.cmake

@@ -148,6 +148,8 @@ if(NOT Qt5Core_FOUND)
 
         include( ${QT_USE_FILE} )
     endmacro()
+
+    add_definitions("-DQ_DECL_OVERRIDE=override")
 endif()
 
 if( Qt5Core_DIR )

src/mirall/cookiejar.h

@@ -29,7 +29,11 @@ public:
     bool setCookiesFromUrl(const QList<QNetworkCookie> &cookieList, const QUrl &url) Q_DECL_OVERRIDE;
     QList<QNetworkCookie> cookiesForUrl(const QUrl &url) const Q_DECL_OVERRIDE;
 
-    virtual bool deleteCookie(const QNetworkCookie & cookie) Q_DECL_OVERRIDE;
+    bool deleteCookie(const QNetworkCookie & cookie)
+#if QT_VERSION > QT_VERSION_CHECK(5, 0, 0)
+        Q_DECL_OVERRIDE //that function is not virtual in Qt4
+#endif
+    ;
     void clearSessionCookies();
 
 signals: