Mark plugins as experimental for now.
diff --git a/CHANGES.txt b/CHANGES.txt
index f5109a1..383045b 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -20,6 +20,8 @@
code generators. Plugins are just binaries which accept a protocol buffer
on stdin and write a protocol buffer to stdout, so they may be written in
any language. See src/google/protobuf/compiler/plugin.proto.
+ **WARNING**: Plugins are experimental. The interface may change in a
+ future version.
* inf, -inf, and nan can now be used as default values for float and double
fields.