non-production shadow testing?

[dormando]

Just in case:

https://github.com/memcached/memcached/pull/557 - is a pretty major patch.
it can potentially hugely reduce CPU usage on both clients and servers,
cut memory usage for large numbers of connections, fix memory bloats in
some specific situations/etc.

...but it's in a pretty crufty part of the codebase. If any of you have
production systems where you can run a memcached build non-live
(debug/development or ideally "shadowing" production traffic), I'd
appreciate you trying it out ahead of me merging it.

Thanks!
-dormando