the socket API yields wrong Error codes for connect().
The usage of EALREADY and EISCONN are not handled as expected by the BSD socket API.
- in err.h, introduce new LWIP internal error code ERR_ALREADY
- in sockets.c add mapping of EISCONN to the err_to_errno_table array
- in api_msg in function do_connect() give out correct errors ERR_ISCONN and ERR_ALREADY in the correct cases
the socket API yields wrong Error codes for connect().
The usage of EALREADY and EISCONN are not handled as expected by the BSD socket API.