Cleaned up the Z309 ZEO protocol, removing versions from arguments and

return values.  This in turn simplified the client and server
software.

Added code to select different client and server stubs and input
handlers depening on whether the Z309 or earlier protocols are used.

ZODB 3.8 clients can now talk to ZODB 3.9 servers and the other way
around.

src/CHANGES.txt

@@ -22,7 +22,23 @@ New Features
   XXX There are known issues with this implementation that need to be
   sorted out before it is "released".
 
-3.9.0a5 (2008-11-??)
+3.9.0a6 (2008-11-??)
+====================
+
+New Features
+------------
+
+- ZODB 3.9 ZEO clients can connect to ZODB 3.8 servers.
+
+Bug Fixes
+---------
+
+- ZODB 3.8 clients couldn't talk to  ZODB 3.9 servers.
+
+- The history method on ZEO clients failed.
+
+
+3.9.0a5 (2008-11-21)
 ====================
 
 New Features