ssl session caching in memcached

Now in httpd trunk r545379:

Add support for distributed caching of SSL Sessions inside memcached, using apr_memcache, which is present in APR-Util 1.3/trunk.

Configure it like this:

SSLSessionCache memcache:10.0.0.1,10.0.0.2,10.0.0.3

I originally wrote the patch for this back in 2005 at ApacheCon US. Never had time to clean it up and test it… But now we needed it for work.

As with anything using memcache, there is no authentication — so only use this if your memcache nodes are on a trusted network — because this could let someone hijack an SSL Session, and that could be bad.