native-activity: Fix InputAvailable support

"native-activity" builds were recently broken by bb8eeb705c which
this patch fixes.

The na-mainloop example has also been updated to verify this by
reducing the fake "render" timeout and also triggering a fake
render when an InputAvailable event is received.

Fixes: #12

examples/na-mainloop/src/lib.rs

@@ -11,7 +11,7 @@ fn android_main(app: AndroidApp) {
 
     while !quit {
         app.poll_events(
-            Some(std::time::Duration::from_millis(500)), /* timeout */
+            Some(std::time::Duration::from_secs(1)), /* timeout */
             |event| {
                 match event {
                     PollEvent::Wake => {
@@ -49,6 +49,9 @@ fn android_main(app: AndroidApp) {
                             MainEvent::RedrawNeeded { .. } => {
                                 redraw_pending = true;
                             }
+                            MainEvent::InputAvailable { .. } => {
+                                redraw_pending = true;
+                            }
                             MainEvent::LowMemory => {}
 
                             MainEvent::Destroy => quit = true,