softpipe: add image support to softpipe (v3)

This adds support for ARB_shader_image_load_store to softpipe.

v2: add RESQ support (Ilia)
v3: constify, cleanup internals, add some comments (Brian).

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