- Refactor the code related to killing requests.
- Free the pins when destroying killed requests (otherwise memory will
leak).
- Customfont texts have associated requests, so those need to be killed
if the font goes away.
Kill requests depending on bitmaps and palettes going away, to avoid
having the emulator crash if there is a request using those bitmaps
and palettes in flight while Lua VM is reset.
Noticed by FatRatKnight.
