Change the logic in g_socket_listener_add_inet_port() as per the
reasoning in the bug report.
- If the OS supports neither IPv6 or IPv4, fail.
- If the OS supports only IPv6, do that.
- If the OS supports only IPv4, do that.
- If the OS supports IPv6 and IPv6 "speaks" IPv4 then bind it
and be done.
- If the OS supports IPv6 and IPv6 doesn't "speak" IPv4 then
create an additional socket for IPv4.
- If binding any socket fails then fail the entire call.
Also, remove the ability to call this function with port == 0. This
is a useless thing to do anyway since you have no way to know what
port number was actually allocated. We should have a separate
function to deal with this.
The whole protocol name thing is pretty weird. The getprotobyname functions
seem to only specify one mapping for name <-> ids, so all families/types
must use the same values. Plus the values used for the protocols are
standardized by IANA, so are always the same.
So, we drop using names for protocols, intead introducing an enum with
a few commonly availible and used protocols.
