Changes

Add custom error display for platforms
Implemented currently for 3DS and SDL2. Switch and Vita are possible,
however an Error report might be generated on Switch (bad, could get
send to big N) and for Vita one would need to match framebuffer format
and such when dealing with GXM for dialog display. This is not worth
currently, since we likely migrate away from vita2d library in the
future.
Go through platform teardown code. While this may not work for every
case (e.g. out of memory on Wii), this should be cleaner.
 (commit: a909dd0)