ir_to_mesa: Handle shadow compare w/projection and LOD bias correctly

ir_to_mesa: Handle shadow compare w/projection and LOD bias correctly

The code would previously handle the projection, then swizzle the
shadow comparitor into place.  However, when the projection is done
"by hand," as in the TXB case, the unprojected shadow comparitor would
over-write the projected shadow comparitor.

Shadow comparison with projection and LOD is an extremely rare case in
real application code, so it shouldn't matter that we don't handle
that case with the greatest efficiency.

NOTE: This is a candidate for the stable branches.

Reviewed-by: Brian Paul <brianp@vmware.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=32395