[cairo] Bringing back the dead... RGB16_565

[David Hill]

Carl, thanks for the bug pointers. I will go code diving and see what I 
can pull out of my hat. These are truly an odd range of color depths.

Dave
> Actually, we do have some assertion statements about unsupported xlib
> image formats in the code already. And people do hit them and report
> bugs. I really just want to make all of these bugs go away.
>
> Here are some of the current bug reports:
>
> 	Cairo doesn't support 565 xlib visual
> 	https://bugs.freedesktop.org/show_bug.cgi?id=10461
>
> 	Cairo doesn't support 655 xlib format
> 	https://bugs.freedesktop.org/show_bug.cgi?id=9719
>
> 	Cairo fails with 555 X server visual
> 	https://bugs.freedesktop.org/show_bug.cgi?id=9993
>
> 	cairo doesn't support 8-bit truecolor visuals
> 	https://bugs.freedesktop.org/show_bug.cgi?id=7735
>
> 	Cairo doesn't support 8-bit pseudocolor visuals
> 	https://bugs.freedesktop.org/show_bug.cgi?id=4945
>
> -Carl
>