Use newly added XMesaCopyContext() and drop the GlxSetRenderTables() call
for Xgl, as this is now done inside XMesaForceCurrent(). This leaves xmesaP.h
but only for the declarations of the three XMesa/XFree86 functions. Also,
GlxSetRenderTables() stays but is only used in hw/xgl/glxext/ .
Also drop xf86glxint.h, no longer used.
Depends on mesa commit 7439a36785b6a2783e80a40a96c09db8f56dc2bc of 2007-03-30.