WindowServer: Return richer result when changing resolutions

Now we return a boolean value from set_resolution() in the Compositor
and Screen class. Also, the WindowServer IPC now returns a richer result
after changing the resolution, which can be used in clients later.

Servers/WindowServer/Screen.h

@@ -40,7 +40,7 @@ public:
     Screen(unsigned width, unsigned height);
     ~Screen();
 
-    void set_resolution(int width, int height);
+    bool set_resolution(int width, int height);
     bool can_set_buffer() { return m_can_set_buffer; }
     void set_buffer(int index);