xvfb: add randr support (v2)

[Adam Jackson]

On Thu, 2015-06-18 at 08:28 -0700, Aaron Plattner wrote:

> Not that this patch hurts or anything, but is there any particular
> reason this remote desktop thing is using Xvfb rather than Xorg +
> xf86-video-dummy?  I thought there was an effort to kill off the
> redundant non-Xorg DDXes at some point.

People have had that idea, yes.  If I've ever endorsed it I apologize,
I really don't think it's worthwhile at this point.  I can't actually
replace Xvfb with Xorg unless it's command-line compatible, which is
tough to do because you don't know the driver to load until after
you've parsed argv.  Yes you could fix that by special casing on
argv[0], but it's an instance of the general problem that teaching Xorg
to be like other servers involves adding complexity to hw/xfree86/ to
get it to _stop_ being so much like xfree86.

I'd rather see useful functionality lifted up to the dix level than
shove even more crap into hw/xfree86.

- ajax