Scanning with udp (`-2`) results in bogus messages

When using

hping3 -2 --scan 0-100 192.168.1.1

this results in no open ports detected (even though I know the target has DNS running). Analysis with Wireshark shows that the UDP messages that `hping3` sends contain a bogus length (quite random really).

Note:

This is possibly due to the `scan.c:sender` function not taking the `-2` option into account and only calls `send_tcp()`.