Security: limit TTL=1

[rozhuk-im]

It will be nice to see that udpxy set by default TTL for multicast and unicast sockets to 1, to not allow use it outside LAN.
And nice to see option to able to increase it.

For unicast sockets:

int ttl = 1;		     /*	max = 255 */
setsockopt(s, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));

This for multicast:

u_char ttl = 1;     /*	range: 0 to 255, default = 1 */
setsockopt(s, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));