* port ios winit el2.0 implementation to the new rust-windowing repo
* unimplemented! => unreachable
trailing comma in CFRunLoopTimerCallback
* implement get_fullscreen
* add iOS specific platform documentation. Add a TODO about how to possibly extend the iOS backend to work have methods callable from more than just the main thread
* assert that window is only dropped from the main thread
* assert_main_thread called from fewer places
