Simulator Changes

[Dan Everton]

I've got some SDL simulator changes pending (sound.c is now implemented 
like the actual hardware, backlight works, etc). However committing 
these changes will break the X11 and Win32 sims as the stub 
implementations of these functions are no longer there.

Are their any objections to this? Should I try and keep those other sims 
running? Or has the SDL sim become usable enough that we can deprecate 
the others?

Dan