Add changelog for half-open socket race condition

Author: digitalresistor

CHANGES.txt

@@ -1,6 +1,14 @@
 3.0.1 (unreleased)
 ------------------
 
+- Fix a bug that would lead to Waitress busy looping on select() on a half-open
+  socket due to a race condition that existed when creating a new HTTPChannel.
+  See https://github.com/Pylons/waitress/pull/435 and
+  https://github.com/Pylons/waitress/issues/418
+
+  With thanks to Dylan Jay and Dieter Maurer for their extensive debugging and
+  helping track this down.
+
 - No longer strip the header values before passing them to the WSGI environ.
   See https://github.com/Pylons/waitress/pull/434 and
   https://github.com/Pylons/waitress/issues/432