This was originally part of a single patch which added the extension, and
implemented it for i965 classic. For information about the evolution of the
patch, please see the subsequent commit.

One difference here as compared to the original mega patch is this does build
support for the compute shader query. Since it cannot be tested on any platform,
it will always return NULL for now. Jordan has already written a patch to
address this, and when that patch lands, this logic can be modified.

v2: Fix typo in subject (Brian Paul)
Add checks for desktop gl (Ilia)
Fail for any callers for now (Ilia)
Update QueryCounterBits for new tokens (Ilia)
Jordan: Use _mesa_has_compute_shaders

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

v3: Rebased on patch which adds the proper information to unstub tessellation
shaders.

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