i965/gen7+: Resolve color buffers when necessary.

i965/gen7+: Resolve color buffers when necessary.

Resolve color buffers that have been fast-color cleared:
    1. before texturing from the buffer (brw_predraw_resolve_buffers())
    2. before using the buffer as the source in a blorp blit
       (brw_blorp_blit_miptrees())
    3. before mapping the buffer's miptree (intel_miptree_map_raw(),
       intel_texsubimage_tiled_memcpy())
    4. before accessing the buffer using the hardware blitter
       (intel_miptree_blit(), do_blit_bitmap())

v2: Rework based on the fact that we have decided not to use an
accessor function to protect access to the region.

Reviewed-by: Eric Anholt <eric@anholt.net>