dumb terminal support

[OKUJI Yoshinori]

  Although there remain still things which should be improved
(e.g. the command "terminal" should have a timeout), I have done most
work necessary for serial terminal support. Now my question is whether
dumb terminal support is really required. As Klaus Reichl suggested,
we can make dumb terminal rather functional, but that isn't very
easy. Thus, I'd leave out dumb terminal support, if this is
acceptable. Send comments, if any.

Okuji