[usocket-devel] better SOCKET-CONNECT for SBCL

Current implementation has the following defects:

* The socket stream ends up with a bogus name as it is created before the socket is connected, making things harder to debug than they need to be.

* In case of error, SB-BSD-SOCKETS:SOCKET-CLOSE was not being called with :ABORT T.

* A unwind from SOCKET-CONNECT that didn't go through the handler leaked an FD.

* An innocent non-error SIGNAL for any reason during SOCKET-CONNECT was taken to be a fatal error due to the handler on type T.

* On datagram sockets CONNECTED-P wasn't set.

Attached patch addresses these issues. Not deeply tested, though.

Cheers,

-- Nikodemus