Update php-memcached to 2.2.0.

Changes in 2.2.0:
- Added the OPT_SERVER_TIMEOUT_LIMIT behaviour

Changes in 2.2.0RC1
- Fixes incorrect size when compressing serialized objects
- Fixes endianess of compressed values

Changes in 2.2.0b1
- Reinstate support for libmemcached 0.x series
- Added SASL support to session handler
- Added Memcached::flushBuffers as per GH #78
- Fixes GH #54: Fixed UDP server adding with newer libmemcached
- Fixed PHP bug #65334: (Segfault if uncompress value failed)
- Fixes GH #14: get with cas token fails to fetch all results
- Fixes GH #68: memcached 2.1.0 requires libmemcached 1.0.10
- Fixes GH #69: compiling on CentOS 6.4 with libmemcached 1.0.17
- Merged PR #91: More granular session locking support
- Added session handler settings:
* memcached.sess_number_of_replicas
* memcached.sess_randomize_replica_read
* memcached.sess_remove_failed
* memcached.sess_connect_timeout
- Added support for memcached protocol handlers
- Added Memcached::setBucket for virtual bucket support
- Added support for msgpack serialization
- Memcached::setSaslAuthData returns correct status on success
- Added support for user-defined flags in set and get operations

(fhajny)