socket interfaces: sc_getpeername: initial integration.
    
    Integration of this function into the library has been delayed
    since the AFD ioctl operation, while succeeding, seems to only
    memset the caller's address buffer, and accordingly to never
    copy the remote socket address to it. Callers of sc_getpeername()
    should therefore first check the return value for success -- which
    may be used as indication that the socket is connected -- and then
    test the returned address buffer for validity.