[libkwineffects] Use fully qualified type name for signal

Qt Script Engine isn't particularly smart at resolving namespaces.

Differential Revision: https://phabricator.kde.org/D20733

libkwineffects/kwineffects.h

@@ -1750,7 +1750,7 @@ Q_SIGNALS:
      * @param w The window whose the keep above state was changed.
      * @since 5.15
      **/
-    void windowKeepAboveChanged(EffectWindow *w);
+    void windowKeepAboveChanged(KWin::EffectWindow *w);
 
     /**
      * This signal is emitted when the keep below state of @p was changed.
@@ -1758,7 +1758,7 @@ Q_SIGNALS:
      * @param w The window whose the keep below state was changed.
      * @since 5.15
      **/
-    void windowKeepBelowChanged(EffectWindow *w);
+    void windowKeepBelowChanged(KWin::EffectWindow *w);
 
     /**
      * This signal is emitted when the full screen state of @p w was changed.
@@ -1766,7 +1766,7 @@ Q_SIGNALS:
      * @param w The window whose the full screen state was changed.
      * @since 5.15
      **/
-    void windowFullScreenChanged(EffectWindow *w);
+    void windowFullScreenChanged(KWin::EffectWindow *w);
 
 protected:
     QVector< EffectPair > loaded_effects;