EXT_clip_cull_distance: add GL_OES_shader_io_blocks interaction (#605)

extensions/EXT/EXT_clip_cull_distance.txt

diff --git a/extensions/EXT/EXT_clip_cull_distance.txt b/extensions/EXT/EXT_clip_cull_distance.txt
index c49835e..e83291b 100644
--- a/extensions/EXT/EXT_clip_cull_distance.txt
+++ b/extensions/EXT/EXT_clip_cull_distance.txt
@@ -24,8 +24,8 @@
 
 Version
 
-    Last Modified Date: March 9, 2016
-    Revision: 3
+    Last Modified Date: February 27, 2024
+    Revision: 4
 
 Number
 
@@ -50,6 +50,8 @@
     This extension interacts with OES_geometry_shader and
     EXT_geometry_shader.
 
+    This extension interacts with OES_shader_io_blocks.
+
 Overview
 
     This extension adds support for hardware clip planes and cull
@@ -273,6 +275,7 @@
         highp float gl_CullDistance[];
 
     };
+    If I/O blocks are not in use, these variables are not in gl_PerVertex.
 
     Similar changes in Geometry, Tessellation Control, Tessellation Evaluation
     language "in gl_PerVertex" and "out gl_PerVertex" structures.
@@ -434,6 +437,8 @@
 
     Rev.    Date    Author    Changes
     ----  --------  ------  ---------------------------------
+     4    02/27/24  zmike   Add GL_OES_shader_io_blocks interaction.
+
      3    03/09/16  mribble Clean up QTI names and emails.
 
      2    03/08/16  dkoch   Language consistency and cleanup pass.