Update php_memcached.c

The symbols memcached_server_major_version, memcached_server_minor_version, memcached_server_micro_version have been introduced in libmemcached 1.0.9, not 1.0.9.
Reference: I downloaded the libmemcached source from here:
https://launchpad.net/libmemcached/+download
Merge pull request #68 from giac/patch-1

Fixed compatibility with libmemcached 1.0.8