Fixed compatibility with libmemcached 1.0.8

Fixed execution with libmemcached 1.0.8.
It was throwing: "undefined symbol: memcached_server_micro_version in Unknown on line 0"
That symbol has been introduced in libmemcached 1.0.9, not 1.0.8.
I checked the libmemcached sources here:
https://launchpad.net/libmemcached/+download