Implement getsockopt() for nonblocking connect()

[rpwoodbu]

Currently, an ssh connection failure is not communicated properly to libssh, which means that failed connections simply have to timeout within libssh (only 10 seconds, but still).

This is due to the fact that the socket is non-blocking, which requires getsockopt() to communicate the disposition of the connection, which has not been implemented.

See man connect and search for EINPROGRESS for details.

[rpwoodbu]

Done in SHA 64d0022.