changes.src: document %if error fix

Document the fix for errors inside live %if branches.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/doc/changes.src b/doc/changes.src
index b0768c9..d48c4d3 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -8,6 +8,11 @@
 since 2007.
 
 
+\S{cl-2.12.02} Version 2.12.02
+
+\b Fix preprocessor errors, especially \c{%error} and \c{%warning},
+   inside \c{%if} statements.
+
 \S{cl-2.12.01} Version 2.12.01
 
 \b Portability fixes for some platforms.