term command line changes

[Roland McGrath]

I've just checked in some changes that probably break term.
Someone should find out whether or not it still works.

The changes are to the command line syntax of the translator.  The old
syntax should still work.  But the new preferred syntax is to use switches
for the name (--name/-N) and type (--type/-T).  The type can be omitted and
defaults to hurdio.  If the type is hurdio (or defaulted), the filename
argument can be omitted to use the underlying node.  In this way, a
translator of just /hurd/term --name=/dev/ttymyname could be used on top of
some kind of node that does primitive io.  For example, the console fs
stuff could make its tty nodes have an implicit translator setting like
that so that just opening /dev/cons/blah gets the tty.

term now also works usefully with fsysopts.  The name, type, and argument
(the device or file name) can be changed dynamically with fsysopts.  You
can't do this with the pty types--you can only change from hurdio or device
to hurdio or device.  This ought to be enough to set things up so that the
fancy console does fsysopts /dev/console -Thurdio /dev/ttyv0 once it is up.