[Mesa-dev] shader_time update

[Eric Anholt]

Here's my rebase of Ken's shader_time updates for Haswell, attempting to
incorporate review feedback plus my discomfort with the discussion of
addressing changes (it was superfluous -- the messages we're sending are
the untyped byte offsets same both ways, and the RAW vs RGBA32F in the
surface state doesn't matter).  I hope this accurately reflects review, so
I'd appreciate an ack from ken/paul if they agree.  While doing so, I also
made the simple change I'd been thinking about to reduce the overhead of
shader_time.

Available at the shader_time branch of my tree.