o Add new Audio interface implemented by SDLAudio.

o Create SDLAudio in NewNES, hook into into NES.route().

o Add Samples channel to APU in RP2A03, NES.route() reads from Samples
  and writes to Audio field to output audio samples.

o Remove ResizeEvent from SDLVideo's Run method, this fixes resizing on
  Linux.

o Add one to X-position in OAM for now, this lines up sprites with the
  background.