auto merge of #4570 : Manishearth/servo/android-warn, r=jdm

My local android build is a bit wonky so I'm not sure if all warnings have been fixed, though. I'll try to poke around and fix it.

ports/glutin/window.rs

@@ -33,6 +33,7 @@ use util::cursor::Cursor;
 use std::ptr;
 
 struct HeadlessContext {
+    #[allow(dead_code)]
     context: glutin::HeadlessContext,
     size: TypedSize2D<DevicePixel, uint>,
 }