Merge branch 'i915-unification'

This branch replaces the DRM pool interface used by i915tex with a "dri_bufmgr"
interface in dri/common which may be set up to use either TTM or traditional
static memory management according to what is available.  The i915tex TTM
code now requires an updated DDX which provides proper buffer objects for the
static front/back/depth, instead of using fake buffers.  The driver is now
built as i915_dri.so, and should replace the old i915 driver shortly.