Add ntohll and htonll

Change-Id: Iaf2f8c732ce3ad7ce345f3395eb8a1bd4894ba72
Reviewed-on: http://review.couchbase.org/28814
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>