Allow rawmode (or filemode) to specify '-' (stdin) as the input file.
Allow rawmode (or filemode) to specify '-' (stdin) as the input file.

This allows you to pipe into imagezip ala:
     tar cf - dir-o-stuff | imagezip -f - dir-o-stuff.ndz
But of course this only works with "raw" or "regular file" inputs where we
are not seeking around looking for metadata with which to do intelligent
compression.

nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome