ddns-scripts: add support for dynu.com IPv6 update

Dynu.com already support IPV6 updates using the parameter myipv6, adding to services_ipv6 to enable support in OpenWRT/LEDE

Signed-off-by: Phil John <philjohn@gmail.com>

net/ddns-scripts/files/services_ipv6

@@ -65,6 +65,8 @@
 "dyn.com"		"http://[USERNAME]:[PASSWORD]@members.dyndns.org/nic/update?hostname=[DOMAIN]&myip=[IP]"	"good|nochg"
 "dyndns.org"		"http://[USERNAME]:[PASSWORD]@members.dyndns.org/nic/update?hostname=[DOMAIN]&myip=[IP]"	"good|nochg"
 
+"dynu.com"    "http://api.dynu.com/nic/update?hostname=[DOMAIN]&myipv6=[IP]&username=[USERNAME]&password=[PASSWORD]"
+
 "dynv6.com"		"http://dynv6.com/api/update?hostname=[DOMAIN]&token=[PASSWORD]&ipv6=[IP]"	"updated"
 
 "goip.de"		"http://www.goip.de/setip?username=[USERNAME]&password=[PASSWORD]&subdomain=[DOMAIN]&ip6=[IP]"