Lots of fixes from Philipe Troin:

* Fixed open and creation modes and permissions for QFA and table-of-contents
  files in dump and restore.
* Fixed the archive file descriptor handling enabling it to be 0.  This can
  happen in some cases when shell redirections are used.
* Delayed the opening of archive file until after suid had been dropped (fixing
  a possible security issue if dump is suid).
* Fixed the 'S' command handling in the rmt client part.
* Modified the end-of-tape script handling to print out statistics (and stop
  the timer) before launching the eot script. Also, the eot script does not get
  run anymore when using -M (which makes sense) or when multiple tapes are
  listed on the command line (-f tape0,tape1,tapen) (which also makes sense).