render.c: RGB2 now gets the right color from the RGB color map.

render.c: RGB2 now gets the right color from the RGB color map.
  And a first cut at handling transparancy values properly. However
  to do this we merely needed to

pixmap.[ch]: write our own routines for retrieving a close colormap index
  given a pixel value. Well, and also had to

video_chroma/i420_rgb.[ch]: save the RGB colormap that is allocated.

Modules.am: forgot new pixmap.c

others: more misc abstraction/cleanup