Disable key repeat if key catcher is 0

SDL1.2 branch disables key repeat when key catcher is 0.
Presumably to prevent binds from executing multiple times.

SDL2 replaced being able to disabled key repeat using SDL_EnableKeyRepeat
with a non-zero repeat value in the key event.
Fix ctrl-c etc codes for edit fields
Merge pull request #86 from zturtleman/sdl2_fixes

client: make sdl2 input behavior closer to master, refs #332