handle Android app events in frontend/device code

Events have been passed to the frontend/device (or /input) code before.
Some of them have been handled in the FFI/input code, however. That
seems to be highly critical with regard to timing, though, so we just
let it enqueue the event for our code to process later. That way, a
mutex that locks the input event queue can be freed faster.
update base with simplified Android input code