* Change mds_client_info to mds_export_data and embed it in obd_export.

* Change mds_client_info to mds_export_data and embed it in obd_export.
* Curtail some excessive include cycles.
* Create "phantom" exports from last_rcvd data, suitable for later (soon!)
  hooking up in mds_connect.
* Add class_new_export utility function for use by class_connect and
  mds_read_last_rcvd.
* Fix last_mount/last_rcvd recovery-eligibility test in mds_read_last_rcvd.
* Force common.sh's DEBUG_WAIT read to use /dev/tty, so it works from scripts
  like runtests.  (lconf, take me away!)