i965: Delete duplicate write_timestamp function.

brw_queryobj.c needs a version of write_timestamp that works on all
generations for the QueryCounter() driver hook.  So there's no point in
duplicating it in gen6_queryobj.c.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Eric Anholt <eric@anholt.net>
mesa: Set the correct error in _mesa_BeginConditionalRender

Piglit was recently changed to expect the correct error code (piglit
commit 271b998), so it started failing on Mesa.  This corrects that
failing and adds some spec quotations to justify the errrors set.

The code was rearranged a little bit to match the order listed in the
spec.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
glsl: update stale comment