Add a new policy for when core Specifications and extensions are updated

(internal reference: gitlab opengl/API issue 103).

docs/update_policy.php

@@ -0,0 +1,45 @@
+<?php
+$static_title = 'Khronos OpenGL Specification Update Policy';
+
+include_once("../../../assets/static_pages/khr_page_top.php");
+?>
+
+<p> This page describes policy of the Khronos OpenGL Working Group for
+    updating API and Shading Language Specification documents, as well as
+    extension documents. </p>
+
+<p> This policy was last updated on 2019-03-13. </p>
+
+<h2> Specification Updates </h2>
+
+<p> The current core (OpenGL 4.6, OpenGL ES 3.2, OpenGL SC 2.0, GLSL 4.60,
+    GLSL ES 3.20, and GLX 1.4) documents are updated in response to issues
+    and bugs the OpenGL Working Group considers priorities. The update
+    frequency is irregular and dependent on the accumulated backlog of
+    issues, up to several times per year. </p>
+
+<p> While Khronos publishes older (non-current) Specifications such as
+    OpenGL 4.5 or OpenGL ES 3.0, such Specifications are usually <b>not</b>
+    updated in response to issues and bugs unless there's a compelling
+    reason. One such compelling reason has been to update older OpenGL ES
+    Specifications on which WebGL is based, in response to requests from the
+    WebGL Working Group. </p>
+
+<h2> Extension Updates </h2>
+
+<p> Khronos-approved (<tt>ARB</tt>, <tt>OES</tt>, or <tt>KHR</tt> vendor
+    suffixed) extensions are usually updated when corresponding changes are
+    made to a core Specification, but with some time lag. </p>
+
+<p> This is a recent policy. Older bug fixes to core Specifications have not
+    always been back-ported to the corresponding extensions, and we are
+    unlikely to perform this exercise for closed issues and bugs without
+    compelling reason. </p>
+
+<p> We will tag each Khronos-approved extension with a link to this policy
+    document and a recommendation to refer to the current core Specification
+    for the latest wording. </p>
+
+<?php include_once("../../../assets/static_pages/khr_page_bottom.php"); ?>
+</body>
+</html>

index_es.php

@@ -14,6 +14,8 @@
 
 <p> <b>Table of Contents</b>
 <ul>
+<li> <b><a href="docs/update_policy.php">Working Group Policy</a></b> for
+     when Specifications and extensions will be updated. </li>
 <li> <b><a href="#specs">Current OpenGL ES API and Shading Language
      Specifications and Reference Pages</a></b>
      <ul>

index_gl.php

@@ -18,6 +18,8 @@
 
 <p> <b>Table of Contents</b>
 <ul>
+<li> <b><a href="docs/update_policy.php">Working Group Policy</a></b> for
+     when Specifications and extensions will be updated. </li>
 <li> <b><a href="#apispecs">Current OpenGL API, Shading Language, GLX,
      and Related Specifications and Reference Pages</a></b> </li>
 <li> <a href="#headers">Core API and Extension Header Files</a> </li>

index_sc.php

@@ -17,6 +17,8 @@
 <p> The current version of OpenGL SC is OpenGL SC 2.0. </p>
 
 <ul>
+<li> <b><a href="docs/update_policy.php">Working Group Policy</a></b> for
+     when Specifications and extensions will be updated. </li>
 <li> OpenGL SC 2.0
      <a href="specs/sc/sc_spec_2.0.pdf">
      Full Specification </a> (version 2.0.0, April 19, 2016). </li>