Drop GLcore dependency from glx module.
Work around double destroy case and add DRIUnlockedCallback() function.
New files, lots of code coming from GL/mesa/X/xf86glx.c and the libGL
loader code.
Add XSERV_t, TRANS_SERVER, TRANS_REOPEN to quash warnings.
Add #include <dix-config.h> or <xorg-config.h>, as appropriate, to all
source files in the xserver/xorg tree, predicated on defines of
HAVE_{DIX,XORG}_CONFIG_H. Change all Xfont includes to
<X11/fonts/foo.h>.
