Switch from trivial-sockets to usocket

[Erik Huelsmann]

Currently, the library depends on trivial-sockets, but to make DCC work, we need to switch to usocket. That library has functions to retrieve more information on either the remote and local tcp connection sides.

This switch really becomes worthwhile when usocket supports tcp-connection listening sockets, to support the active initiation of DCC connections.

(In the current version of usocket, both accepting DCC connections and the initiation of passive connections could be supported; just not active initiation.)