AES encryption support

[Vincent--]

Since libmemcached v1.0.6, support for transparent AES encryption is available

As suhosin doesnt seem to be maintained anymore and there no real alternative for php7, is it doable to add AES encryption for session in php-memcached? Happy to work on it if people are interested but I'm not PHP/C expert 😬

[sodabrew]

It's just a matter of exposing the memcached_set_encoding_key() function into PHP. Pull Requests certainly welcomed! http://docs.libmemcached.org/libmemcached-1.0/memcached_set_encoding_key.html