Perhaps pound can take the following  approach to this problem:

Apache 2.0.55 changelog:
...
  *) proxy HTTP: If a response contains both Transfer-Encoding and a
     Content-Length, remove the Content-Length and don't reuse the
     connection, mitigating some HTTP Response Splitting attacks.
     [Jeff Trawick]
...

For proxies, I think this will become the defacto standard way of 
dealing with this security risk.