Fix udp:setpeername("*")

There seems to be a curious difference between MacOS and
Linux and I am not sure if this is documented. When you
break a "connection" on Mac OS, you only eliminate the peer
association, but the local address remains bound. On Linux,
breaking a "connection" eliminates the binding to the local
address. Have you guys ever come accross this?

Another irritating difference is that connect() returns the
error EAFNOSUPPORT on Mac OS. I am going to ignore all
errors when the reason for calling connect() is simply to
break the "connection".

src/inet.h

@@ -29,6 +29,7 @@ const char *inet_tryconnect(p_socket ps, const char *address,
         const char *serv, p_timeout tm, struct addrinfo *connecthints);
 const char *inet_trybind(p_socket ps, const char *address, const char *serv,
         struct addrinfo *bindhints);
+const char *inet_trydisconnect(p_socket ps, int family, p_timeout tm);
 
 int inet_meth_getpeername(lua_State *L, p_socket ps, int family);
 int inet_meth_getsockname(lua_State *L, p_socket ps, int family);