[wwwdocs] Mention the GNU C enum changes in gcc-13/changes.html

[Jakub Jelinek <jakub@redhat.com>]

Hi!

The following patch attempts to document the PR36113 changes to the
GNU C extension support of enumerators which don't fit into int.

Ok for wwwdocs?

Shall we mention it in porting_to.html as well?
The only known affected package is (was?) the Linux kernel.

diff --git a/htdocs/gcc-13/changes.html b/htdocs/gcc-13/changes.html
index f8e9560c..d2035435 100644
--- a/htdocs/gcc-13/changes.html
+++ b/htdocs/gcc-13/changes.html
@@ -59,6 +59,22 @@ a work-in-progress.</p>
       <a href="https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/ARM-iWMMXt-Built-in-Functions.html">
       iWMMXt built-in functions</a>.
     </li>
+    <li>The behavior of the GNU C extension support of enumerators which
+      don't fit into <code>int</code> has been changed to match the C2X
+      behavior.  Previously, in enumerations where at least one enumerator
+      didn't fit into <code>int</code>, only those enumerators that didn't
+      fit into <code>int</code> had the <code>enum</code> type and others
+      had <code>int</code> type and while the <code>enum</code> is being
+      defined enumerators that didn't fit into <code>int</code> had some
+      unspecified type with the sign and precision of its value.
+      In GCC13, in such enumerations all enumerators have the
+      <code>enum</code> type and while the <code>enum</code> is being
+      defined enumerators that didn't fit into <code>int</code> have
+      type of their value.  If all enumerators fit into <code>int</code>
+      type, as before all enumerators have <code>int</code> type, both
+      while the <code>enum</code> is being defined and after it is defined.
+      See <a href="https://gcc.gnu.org/PR36113">PR36113</a> for details.
+    </li>
 </ul>
 
 

	Jakub