i965/gen6+: Enable arb_transform_feedback_overflow_query.

This extension adds new query types which can be used to detect overflow
of transform feedback buffers. The new query types are also accepted by
conditional rendering commands.

v3:
    - s/gen7+/gen6+/ in the relnotes (Jordan Justen)

Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
diff --git a/docs/features.txt b/docs/features.txt
index 01315a0..346ba28 100644
--- a/docs/features.txt
+++ b/docs/features.txt
@@ -303,7 +303,7 @@
   GL_ARB_sparse_texture2                                not started
   GL_ARB_sparse_texture_clamp                           not started
   GL_ARB_texture_filter_minmax                          not started
-  GL_ARB_transform_feedback_overflow_query              not started
+  GL_ARB_transform_feedback_overflow_query              DONE (i965/gen6+)
   GL_KHR_blend_equation_advanced_coherent               DONE (i965/gen9+)
   GL_KHR_no_error                                       not started
   GL_KHR_texture_compression_astc_hdr                   DONE (core only)