Include charset number for cache entry hashing. This should prevent serving result
sets which have the wrong charset.
API change: get_hash_key expects new "charsetnr" (int) parameter after "port".
API change: changing is_select() signature from bool is_select() to
mixed is_select(). Mixed can be either boolean or
array(long ttl, string server_id). This is needed by PECL/mysqlnd_ms.
Other
Support acting as a cache backend for
PECL/mysqlnd_ms 1.3.0-beta or later
to transparently replace MySQL Replication slave reads with cache accesses,
if the user explicitly allows.