corrections to network handling

 - access.c: isLocalAddress(): there were several checks
   against localhost address; however, the checks applied
   equally to any local address of the XDM host, so a check
   was created to check an address against any of the
   addresses assigned to interfaces of the XDM host.

 - access.c: scanHostList(): check local address better with
   the isLocalAddress() function.

 - access.c: ForEachMatchingIndirectHost(): check local
   address better with the isLocalAddress() function.

 - policy.c: Accept(): the entire ACL was bypassed because
   Accept() always returned NULL (permitting access).  The
   Accept() function was reworked to perform the same
   address and host based checks as Willing().

 - policy.c: SelectConnectionTypeIndex(): this function was
   previously only selecting the first item in the list that
   was a usable address.  Unfortunately, Xorg servers place
   interface addresses in the list in rather arbitrary order
   and do not check whether the address is accessible.

   This was reworked to favor connections in the list that
   match the address on which the XDMCP Request packet was
   received.  Also, if there are no viable addresses in the
   list and the XDMCP Request packet was received from one
   of our own addresses, use that address.

   This should also probably be reworked to favor an address
   that corresponds to the address that we would normally
   use for connecting to the remote host by name.

 - xdmcp.c: request_respond(): reworked to pass additional
   information to Accept() and SelectConnectionTypeIndex().
strap out DNS spoofing actions

- getaddrinfo() returns addresses suitable for connect.  Not
  all addresses that are valid for receive are suitable for
  connect: case in point is IPv4 link local addresses where
  a normal address is also assigned to the remote host.  So,
  for, example:

    169.254.7.223 -> linux-4.local
    linux-4.local -> 192.168.0.14