Signal catcher to catch those signals sent on keystrokes.

Actually found a better way while researching this, and this all gets deleted.
I wanted to save this version in the git history though.
Revert the signal catcher code as promised.
Better way to deal with the signals, tell the terminal not to send them.
Document the terminal use of control characters.
Fix memory corruption.
Fix parsing the final CSI parameter.
Deal with terminal resize.

NOTE - not actually triggering this yet, and it's still slightly buggy.