libceph: message signature support

Signed-off-by: Yan, Zheng <zyan@redhat.com>

diff --cc fs/ceph/mds_client.c
Simple merge

diff --cc include/linux/ceph/auth.h
Simple merge

diff --cc include/linux/ceph/ceph_features.h
Simple merge

diff --cc include/linux/ceph/messenger.h
Simple merge

diff --cc include/linux/ceph/msgr.h
Simple merge

diff --cc net/ceph/auth_x.c
Simple merge

diff --cc net/ceph/messenger.c
Simple merge

diff --cc net/ceph/osd_client.c
Simple merge