i965: Add support for EXT_timer_query on Ironlake.

We could potentially do this on G45 as well, though the units are
different.  On 965, the timestamp is tied to hclk, which would make
supporting it harder.

docs/relnotes-7.9.html

@@ -34,6 +34,7 @@ tbd
 
 <h2>New features</h2>
 <ul>
+<li>GL_EXT_timer_query extension (i965 driver only)
 </ul>