docs: GL_ARB_provoking_vertex

docs/relnotes-7.7.html

@@ -37,6 +37,7 @@ tbd
 <li>GL_ARB_draw_elements_base_vertex (supported in Intel i965 and software drivers)</li>
 <li>GL_ARB_depth_clamp (supported in Intel i965 DRI and software drivers)</li>
 <li>GL_NV_depth_clamp (supported in Intel i965 DRI and software drivers)</li>
+<li>GL_ARB_provoking_vertex (same as GL_EXT_provoking_vertex)</li>
 </ul>