The first fbconfig which has a depthbuffer > 0 and doublebuf is choosen
when associating fbconfigs with the visuals, indepenent of stencil bits.
This happens to work ok on intel as there all fbconfigs with a
depthbuffer > 0 also have stencil bits.
This patch fixes this by first trying to get a fbconfig for default X visuals
with both stencilbuf, depthbuf and doublebuffering, and if that fails fallback
to trying to get one with only a depthbuf and doublebuffering.