Lots of changes:

Lots of changes:
	- use the new interface to the software rasterizer.
	- manage all fallbacks internally, hooking in swrast or
	  swrast_setup if necessary.
	- removed lots of marginal code no longer appropriate in a
	  maturing driver.
	- reworked the vertex-setup and triangle routines, including
	  drawing unfilled triangles from within the driver.