XDDMCP performs multi-host transfer

This commit pretty much gets xddmcp working.  Unfortunately,
XDD seems to be fairly buggy.  So now it's a matter of restoring
previous XDD functionality.
XDDMCP multi-host port fix

The problem with multi-host transfers with xddmcp was that the
ports were not being correctly skipped.  This is now fixed,
and multi-host transfers work.