Dispatch read one byte of the code, so a code with a non-zero high byte
was handled as its low byte. Message::get_message_code now reads the
whole little-endian uint32 and handlers register by u32. PeerInit and
PierceFirewall, the only frames with a one-byte code, get their own
accessor for the listener's first frame.
Wire the incoming server FileSearch (code 26): the handler now forwards
ServerMessage::FileSearchRequest -> ClientOperation::IncomingSearch instead of
just logging. The client matches the query against its shares and, if anything
matches, sends a FileSearchResponse to the searcher — connecting to them first
(GetPeerAddress -> outbound P) and flushing the response on PeerConnected when
not already connected. GetPeerAddressResponse now also caches peer addresses
for the serve path. Adds build_search_response + a unit test.
Michel de Graaf