doc/changes.src: retroactively document anonymous %push

Retroactively document the anonymous %push, which was added in version
2.04 but not documented.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/doc/changes.src b/doc/changes.src
index 00b6076..cf20fc3 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -112,6 +112,9 @@
   when disabled, but doesn't optimize.  This allows most forward references
   to be resolved properly.
 
+\b \c{%push} no longer needs a context identifier; omitting the context
+  identifier results in an anonymous context.
+
 
 \S{cl-2.03.01} Version 2.03.01