libceph: update rados.h

libceph: update rados.h

Update most of "include/linux/ceph/rados.h" to match its user space
counterpart in "src/include/rados.h" in the ceph tree.

Almost everything that has changed is either:
    - added or revised comments
    - added definitions (therefore no real effect on existing code)
    - defining the same value a different way (e.g., "1 << 0" vs "1")

The only exceptions are:
    - The declaration of ceph_osd_state_name() was excluded; that
      will be inserted in the next patch.
    - ceph_osd_op_mode_read() and ceph_osd_op_mode_modify() are
      defined differently, but they were never used in the kernel
    - CEPH_OSD_FLAG_PEERSTAT is now CEPH_OSD_FLAG_PEERSTAT_OLD, but
      that was never used in the kernel

Anything that was present in this file but not in its user space
counterpart was left intact here.  I left the definitions of
EOLDSNAPC and EBLACKLISTED using numerical values here; I'm
not sure the right way to go with those.

This and the next two commits resolve:
    http://tracker.ceph.com/issues/4164

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>