[Users] ";user=phone"

[Mark Kent]

An upstream PSTN-gateway provider wants 
SIP Request-URIs in this format:

  INVITE sip:16509411212 at x.y.z.w;user=phone SIP/2.0

To achieve this, I did:

  rewritehostport("x.y.z.w;user=phone");
  t_relay();

which works, but makes me uneasy as the stuff after the ";"
isn't really the host or the port.  What is the official way
to put "user=phone" on the end?

Thanks,
-mark