XIDs for GLX visuals and FBConfigs used to be interchangable and the list of
GLX visuals was identical to the list for FBConfigs. This patch splits handling
of these two data types and allows the X server to pick and choose the FBConfigs
that are exposed as visuals.
When available, use the 2D driver texOffsetStart hook and the 3D driver
setTexOffset hook to save the overhead of passing the pixmap data to
glTex(Sub)Image.
The basic idea is to update the driver specific 'offset' for bound pixmaps
before dispatching a GLX render request and to flush immediately afterwards
if there are any pixmaps bound. This should ensure that the 3D driver can
use pixmaps for texturing directly regardless of the X server moving them
around.
