glsl: Extend lowering pass for gl_ClipDistance to support other arrays (v4)

glsl: Extend lowering pass for gl_ClipDistance to support other arrays (v4)

This will come in handy when we want to lower gl_CullDistance into
gl_CullDistanceMESA.

[airlied: drop separate APIs for clip/cull - just use single API
to call both passes.]

v3: reexamine my sanity, this was pretty broken, the new code
creates one copy of gl_ClipDistanceMESA, as the clip distance
varying and lowers everything into that in two passes, one for clips
one for culls.
v4: rework using the passes in clip/cull sizes, instead of the
array sizes.

Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>