o Use float32 instead of uint32 for Cycles chans so PAL support will be
easier.  On PAL, the PPU executes 3.2 cycles per 1 CPU cycle instead of
3.

o Add -cpu-profile/-mem-profile switches which generate profile files
for use with 'go tool pprof'.

o Pull out FPSManager into its own file as new FPS type.  This allows
nintengo to throttle the framerate independent of the SDL code.

o Add 9/0 as shortcuts to enable/disable the background/sprites
dynamically.