!UPSTREAM: i965/gen7+: Create helper functions for single-sample MCS buffers.

TODO:

- comment change should move to SURFACE_STATE patch
!UPSTREAM: i965/gen7+: Allocate MCS buffers for use by fast color clears.

TODO:

- write blorp code to do fast color clears

- write blorp code to do color resolves

- write code to ensure that color resolves happen when necessary

- write code to do fast rather than slow color clears when possible