changes.src: document if for %ifmacro.

Document fixed %ifmacro.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/doc/changes.src b/doc/changes.src
index 2d8b850..f718a94 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -19,6 +19,8 @@
 
 \b Support for thread-local storage in ELF32 and ELF64.  See \k{elftls}.
 
+\b Fix crash on \c{%ifmacro} without an argument.
+
 
 \S{cl-2.05.01} Version 2.05.01