Some source files updated to call _mesa_debug(), but not finished.
Added __GLimports as a parameter to _mesa_create/init_context() and
updated drivers accordingly.
Fleshed-out more of the __GLimports and __GLexports functionality.
Removed run-time config file support (config.c)
instead of passing a GLcontext* to ResizeBuffers(), pass a GLframebuffer*.
The idea is that a window can be resized without it being bound to a rendering
context. This makes for a nice clean-up in the XFree86 server-side GLX code.
Renamed ctx->Driver.ResizeBuffersMESA() to ctx->Driver.ResizeBuffers().
