xmame: switch to x11 backend(to improve scaling performance on xv-enabled devices)

xmame: switch to x11 backend(to improve scaling performance on xv-enabled devices)

On nokia900 the sound has issues and CPU usage is 100% with the SDL backend
  when scalling the game to fullscreen
Using XV and MIT-SHM seem to improve performances:

With SDL:
  SDL found mode:800x480x16
  SDL found mode:800x480x16
  SDL: Using a mode with a resolution of: 800x480x16
  Initialized no effect: bitmap depth = 16, color format = RGB 565
  info: audiodevice (null) set to 16bit linear stereo 44100Hz
  info: sysdep_dsp: using sdl plugin
  info: dsp: using timer-based audio
  Average FPS: 16.623416 (988 frames)

With X11,XV,MIT-SHM:
  MIT-SHM & XV Extensions Available. trying to use.
  Can't find a suitable RGB format - trying YUY2 instead.
  XInput: Initialization...
  Initialized no effect: bitmap depth = 16, color format = YUY2
  Clearing YUY2
  Using Xv & Shared Memory Features to speed up
  info: set to 16bit linear stereo 44100Hz
  info: sysdep_dsp: using alsa plugin
  info: sysdep_mixer: using alsa plugin
  Average FPS: 23.254317 (828 frames)

The nokia900 has an omap SOC, that means that it can uses omapfb,
  which support xv, so using XV improve the performances in the case
  of the nokia900

And in the case where XV is not available
(XV disabled for testing purposes, still on nokia900):
  XInput: Initialization...
  MIT-SHM Extension Available. trying to use... Success.
  Using Shared Memory Features to speed up
  Initialized no effect: bitmap depth = 16, color format = RGB 565
  info: set to 16bit linear stereo 44100Hz
  info: sysdep_dsp: using alsa plugin
  info: sysdep_mixer: using alsa plugin
  Average FPS: 18.793345 (1267 frames)

Which is a bit faster than SDL.

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@no-log.org>