Removed memcached.sess_consistent_hashing option.

1. Removed memcached.sess_consistent_hashing which is a lesser version  of memcached.sess_consistent_hash
2. Added default value for memcached.sess_consistent_hash
Merge branch 'FixIssue53' of https://github.com/Vendini/php-memcached into Vendini-FixIssue53

Conflicts:
	php_memcached.h
	php_memcached_session.c