i965/gs: Implement support for geometry shader surfaces.

i965/gs: Implement support for geometry shader surfaces.

This patch implements pull constant upload, binding table upload, and
surface setup for geometry shaders, by re-using vertex shader code
that was generalized in previous patches.

Based on work by Eric Anholt <eric@anholt.net>.

v2: Update ditry bits for brw_gs_ubo_surfaces to account for commit
77d8fbc (mesa: add & use a new driver flag for UBO updates instead of
_NEW_BUFFER_OBJECT).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>