There is a problem with some fonts that the height necessary
to store the font is greater than the max texture size, which
causes a fallback to occur. We can avoid this by storing two
macro columns side-by-side in the texture and adjusting
the calculations to suit.

This fixes
xfd -fn -*-*-*-*-*-*-*-*-*-*-*-*-*-*
falling back here, when it picks
-arabic-newspaper-medium-r-normal--32-246-100-100-p-137-iso10646-1

Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>