Merge pull request #278 from hfink-daqri/gl-mesa-egl-sync

Add GL_MESA_EGL_sync extension
diff --git a/xml/gl.xml b/xml/gl.xml
index a2b33d0..8a325e3 100644
--- a/xml/gl.xml
+++ b/xml/gl.xml
@@ -79,7 +79,18 @@
         <type>typedef void (<apientry/> *<name>GLVULKANPROCNV</name>)(void);</type>
-    <!-- SECTION: GL parameter class type definitions. -->
+    <!-- SECTION: GL parameter class type definitions.
+         The groups are intended to contain all the possible legal values
+         for corresponding function parameters, but it is likely that many
+         of the groups are out of date relative to current OpenGL and OpenGL
+         ES specifications, and the many extensions to those specifications.
+         As such, they may not be a reliable source for enumeration info.
+         We welcome assistance from the community in achieving and
+         maintaining the completeness of the enum groups. Khronos does not
+         use the enum group information, and the OpenGL Working Group does
+         not have internal resources to bring it up to date.
+    -->
         <group name="EvalMapsModeNV">