GRIM: Use exceptions instead of jumps

This probably won't go in, but it was interesting figuring out that it just uses setjmp and longjmp like c++ exceptions.

This lets us get rid of some forbidden symbols, but ScummVM does not allow exceptions, so we probably can't use this. I mainly wanted to start some discussion on if there is any point in doing this.

Also, looking at lua 5.1 it uses exceptions in C++, but setjmp and longjmp for C.