Implement NEO protocol handshaking and use it in newly provided DialLink
and ListenLink which correspondingly first do regular network dial or
listen and than perform the handshake on just established TCP
connection. If handshake goes ok, the result is wrapped into NodeLink.

Some history:

	lab.nexedi.com/kirr/neo/commit/8d0a1469	X Handshake draftly done

See also http://navytux.spb.ru/~kirr/neo.html#development-overview
(starting from "The neonet module also provides DialLink and ListenLink
...")