When a phone call or an alarm triggers on iOS, the application receives
an "audio interruption" and it's up to the application to resume
playback when the interruption ends. I added handling for audio
interruptions same as if the game is focused out and then back in.
Using `misc/scripts/fix_headers.py` on all Godot files.
Some missing header guards were added, and the header inclusion order
was fixed in the Bullet module.
