provide this signal as well, as it was the only desktopy thing still be relied on that Corona didn't provide

svn path=/trunk/KDE/kdelibs/; revision=881720

corona.h

@@ -135,7 +135,7 @@ public:
      * behavior should override this method.
      */
     virtual QRegion availableScreenRegion(int id) const;
-    
+
     /**
     * Reccomended position for a popup window like a menu or a tooltip
     * given its size
@@ -218,6 +218,11 @@ Q_SIGNALS:
      */
     void configSynced();
 
+    /**
+     * This signal inicates that a change in available screen goemetry occured.
+     */
+    void availableScreenRegionChanged();
+
 protected:
     /**
      * Loads the default (system wide) layout for this user