changes.src: document %{:} macro parameter range fix

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
diff --git a/doc/changes.src b/doc/changes.src
index 586b8bb..f33e3ce 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -15,6 +15,9 @@
 
 \b Some documentation improvements and cleanups.
 
+\b Fix the handling of macro parameter ranges (\c{%\{:\}}), including
+with brace-enclosed original arguments.
+
 \S{cl-2.15.01} Version 2.15.01
 
 \b Fix building the documentation from the release archive. For 2.15,