It seems to be possible for a user to back out of a screen before
receiving the "dialog completed" callback on Android, in which case
things pointed to by the callback might be gone.
In this case, it's better to simply not call the callback, rather than
crashing.
This is accomplished by assigning "Tokens" to screens that cause
requests, and in ~Screen, invalidate any pending requests belonging to
that token.
Buildfixing
Move some file util files
Buildfix
Move KeyMap.cpp/h to Core where they belong better.
libretro buildfix attempt
Move ini_file
More buildfixes
