More cleanup work on permissions restore:

More cleanup work on permissions restore:
  * Rename some variables/functions/etc to try to make things clearer.
  * Add separate flags to control fflag/acl restore
  * Collect metadata restore into a single function for clarity
  * Propagate errors in metadata restore back out to the client
  * Fix some places where errors were being returned when they
    shouldn't and vice-versa
  * Modes are now always restored; ARCHIVE_EXTRACT_PERM just controls
    whether or not umask is obeyed.
  * Restore suid/sgid bits only if user/group matches archive
  * Cache the last stat results to try to reduce the number of stat calls