i965/state: Support multiple pipelines in brw->num_atoms

i965/state: Support multiple pipelines in brw->num_atoms

brw->num_atoms is converted to an array, but currently just an array
of length 1.

Adds brw_copy_pipeline_atoms which copies the atoms for a pipeline,
and sets brw->num_atoms[p] for pipeline p.

v2:
 * Rename brw->atoms[] to render_atoms
 * Rename brw_add_pipeline_atoms to brw_copy_pipeline_atoms
 * Rename brw_pipeline_first_atom to brw_get_pipeline_atoms

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>