Make the way FSM options are processed easier to read by using structures

Make the way FSM options are processed easier to read by using structures
instead of u_char *.

The changes are cosmetic except:

  RecvConfigAck() now displays the options that are being ACK'd
  Huge (bogus) options sent from the peer won't cause an infinite loop
  SendIdent and ReceiveIdent are displayed consistenlty with other FSM data
  LCP AUTHPROTO options that aren't understood are NAK'd, not REJ'd