WIP: Let signals do their job

So as it is now, signal_handler calls a lot of non-reentrant functions and even exits (making the signal useless). This is a quickie to fix that behavior. Of course, this means you can't have fancy messages and pop-up windows telling you what's wrong. Atleast, the SDL window function would have to be looked into to see if it's reentrant--I suspect it isn't. If you must have messages, you could always use write too.

Tested and core dumped on

uname -a
Linux mik 4.18.16-arch1-1-ARCH #1 SMP PREEMPT Sat Oct 20 22:06:45 UTC 2018 x86_64 GNU/Linux