[BUG] stream_sock: use get_addr_len() instead of sizeof() on sockaddr_storage

[BUG] stream_sock: use get_addr_len() instead of sizeof() on sockaddr_storage

John Helliwell reported a runtime issue on Solaris since 1.5-dev5. Traces
show that connect() returns EINVAL, which means the socket length is not
appropriate for the family. Solaris does not like being called with sizeof
and needs the address family's size on sockaddr_storage.

The fix consists in adding a get_addr_len() function which returns the
socket's address length based on its family. Tests show that this works
for both IPv4 and IPv6 addresses.