(Using GLSL 1.30 or newer)
The width/height members of xRectangle are unsigned, but they were
being interpreted as signed when converting to floating point for the
vertex shader, producing incorrect drawing for values > 32767.
v2:
* Use separate GL_UNSIGNED_SHORT vertex attribute for width/height.
(Eric Anholt)
Reviewed-by: Eric Anholt <eric@anholt.net>