Update sdl.hpp

Forgot __cdecl is visual studio only, but since it's the default calling convention, we don't need to specify it. I put it there to match the SDL definition, heh.
Merge pull request #2 from beannaich/patch-1

Patch 1
more updates for famicom

tried to add per-cycle /RDY checks, but it caused the whole system to
lock up. need to try again tomorrow.
added an abstraction for standard controllers, will implement their
logic once i get an input backend working.
Merge pull request #2 from beannaich/master

Update