ECP patches from Frank Cusack:

- If encryption is required, don't bring up IP/IPv6/IPX until the
  encryption negotiation has completed.
- Shut down LCP if the peer sends an LCP ConfRej instead of CCP ConfRej
  to our MPPE offer.  This fixes a bug where the server could not enforce
  use of encryption in some cases.
- Don't send the M=<message> part of an MS-CHAPv2 success packet to peers
  that don't know how to deal with it.  This allows pre-win2k systems to
  authenticate.
- Don't shut down lcp if MPPE was present in peer's CCP offer along with
  other options.  This allows pre-win2k systems to do MPPE (they offer
  Stac LZS with MPPE).
- Add the beginnings of ecp.c.
- Other minor changes.