Currently only for gl/glsl/vulkan. However, rather than futzing with
con_width and con_height (and trying to guess good values), con_scale
(currently an integer) gives consistent pixel scaling regardless of
window size.
I had forgotten that the cl structs in nq and qw were different layouts,
which resulted in qw's sbar/hud being quite broken. Rather than messing
with the structs, I decided it would be far better in the long run to
clean up sbar's access to the cl struct and the few other nq/qw specific
globals it used. There are still plenty of bugs to fix, but now almost
everything is in the one place.
