softpipe: add ARB_texture_cube_map_array support (v1.1)

softpipe: add ARB_texture_cube_map_array support (v1.1)

This adds support to the softpipe texture sampler and tgsi exec.

In order to handle the extra input to the texture sampling,
I've had to expand the interfaces to take a c1 value for storing
the texture compare value for the TEX2 case.

v1.1: add comments (Brian)

Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>