misc: Add drop_privs component
misc: Add drop_privs component

Many things POX can do these days require having special capabilities
(e.g., creating tap interfaces).  The easiest way to do this is to
run as root, but you may not want to leave POX running as root.

This component lets you start POX as root, but have it transition
to another user.  It currently does this when POX transitions to
the "Up" state, by which other compoents will hopefully have done
everything that needs root powers.

MurphyMc/pox,MurphyMc/pox,MurphyMc/pox,MurphyMc/pox,MurphyMc/pox