i965: Map GL_PATCHES to 3DPRIM_PATCHLIST_n.

i965: Map GL_PATCHES to 3DPRIM_PATCHLIST_n.

Inspired by a patch by Fabian Bieler.

Fabian defined a _3DPRIM_PATCHLIST_0 macro (which isn't actually a valid
topology type); I instead chose to make a macro that takes an argument.
He also took the number of patch vertices from _mesa_prim (which was set
to ctx->TessCtrlProgram.patch_vertices) - I chose to use it directly to
avoid the need for the VBO patch.

v2: Change macro to 0x20 + (n - 1) instead of 0x1F + n to better match
    the documentation (suggested by Ian).

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>