land b_merge on b_devel. Includes b_mount and b_orphan, which includes:

land b_merge on b_devel.  Includes b_mount and b_orphan, which includes:

 - orphans are moved into the PENDING directory for possible recovery
 - replayed opens now open by fid for orphan/rename safety (1042)
 - last close of an orphan inode generates a transno (683)
 - avoid CERROR in normal ll_setattr_raw() error case (1500)

Added code which is currently disabled:

 - dentry pinning from b_mount for cwd and mountpoints (1020)
 - logging code for orphans (and many other things)