Add callback function to allow resize messages to be sent on mac.

src/android/mod.rs

@@ -273,6 +273,9 @@ impl Window {
     pub fn get_api(&self) -> ::Api {
         ::Api::OpenGlEs
     }
+
+    pub fn set_window_resize_callback(&mut self, _: fn(uint, uint)) {
+    }
 }
 
 #[cfg(feature = "window")]