nntpid: Provide proper copyright licence

nntpid: Provide proper copyright licence

Authors are:
 Simon Tatham
 Colin Watson
 Richard Kettlewell
 Ian Jackson

Simon says, in email to me:

  Simon Tatham writes ("Re: nntpid"):
  > Ian Jackson <ijackson@chiark.greenend.org.uk> wrote:
  > > Since IIRC it was yours originally we should probably pick your
  > > preferred licence which AIUI is MIT.
  >
  > It is, yes.

Colin writes on IRC:

02:34 <col> Republic,Diziet: anything DFSG-free is fine by me for my
            nntpid contributions

Richard and me on IRC:

14:44 <Diziet> [Richard]: Oh, speaking of usenet things, did you see the
               email exchange with Simon about nntpid licence ?  Are
               you happy with MIT ?
14:44 <[Richard]> y