Remove OpenGL from Android code

src/os/android.rs

@@ -0,0 +1,25 @@
+#![cfg(any(target_os = "android"))]
+
+use std::os::raw::c_void;
+use Window;
+use WindowBuilder;
+
+/// Additional methods on `Window` that are specific to Android.
+pub trait WindowExt {
+    fn get_native_window(&self) -> *const c_void;
+}
+
+impl WindowExt for Window {
+    #[inline]
+    fn get_native_window(&self) -> *const c_void {
+        self.window.get_native_window()
+    }
+}
+
+/// Additional methods on `WindowBuilder` that are specific to Android.
+pub trait WindowBuilderExt {
+
+}
+
+impl WindowBuilderExt for WindowBuilder {
+}