net/gogoc: new patch with various improvements

• When shutdown, the correct behavior is to send SIGHUP.
• New patch patch-icmp_echo_engine.c: When PID of the gogoc process greater than 65536, it can not perform timeout ping check correctly, due to echo_id in icmp_hdr is declared as uint16_t.
• New patch patch-freebsd.sh: To mute dmesg noise "nd6_dad_timer: cancel DAD on tun0 because of ND6_IFF_IFDISABLED."
• Don't overwrite gogoc.conf on install.

PR: 211426
Submitted by: Clive Lin <clive@tongi.org>
Approved by: maintainer timeout (8 months)