[MEDIUM] moved the sockaddr pointer to the fdtab structure

[MEDIUM] moved the sockaddr pointer to the fdtab structure

The stream_sock_* functions had to know about sessions just in
order to get the server's address for a connect() operation. This
is not desirable, particularly for non-IP protocols (eg: PF_UNIX).

Put a pointer to the peer's sockaddr_storage or sockaddr address
in the fdtab structure so that we never need to look further.

With this small change, the stream_sock.c file is now 100% protocol
independant.