Several fp and vp tweaks:

Several fp and vp tweaks:

	- Renumber VERT_RESULT_* values so that they match the
	  numbers of the corresponding FRAG_ATTRIB_ values.

        - Add ctx->VertexProgram._Current and FragmentProgram._Current
	  values which point to either the current client-supplied
	  program if enabled, or otherwise to the current mesa-internal
	  program.  Thus this program is always the correct one for
	  the current state, providing that the mesa flags to turn on
	  automatic generation are enabled.

	- Add callbacks to ctx->Driver.BindProgram() in texenvprogram.c
	  and t_vp_build.c so that the driver knows when the generated
	  program changes.  This is cleaner than trying to code all the
	  possible _NEW_* flags into the driver, and more precise as well.

	- Add a UsesKill flag to identify fragment programs with that
	  instruction, as these can require special treatment.

	- Move the FRAG_OUTPUT values to mtypes.h, near to similar defn's.