add changelog note about CI_CORE removal
diff --git a/user_guide/changelog.html b/user_guide/changelog.html
index 81514af..1a6cf98 100644
--- a/user_guide/changelog.html
+++ b/user_guide/changelog.html
@@ -111,6 +111,7 @@
 	<li>Core
 		<ul>
 			<li>Changed private functions in CI_URI to protected so MY_URI can override them.</li>
+			<li>Removed CI_CORE boolean constant from CodeIgniter.php (no longer Reactor and Core versions).</li>
 		</ul>
 	</li>
 </ul>