Show external ipv4 address on about screen

src/freedombone-controlpanel

     echo $'IP/DNS addresses'
     echo '================'
     echo ''
-    echo -n "IPv4: $(get_ipv4_address)"
+    echo -n "IPv4: $(get_ipv4_address)/$(get_external_ipv4_address)"
     ipv6_address="$(get_ipv6_address)"
     if [ ${#ipv6_address} -gt 0 ]; then
         echo "    IPv6: ${ipv6_address}"

src/freedombone-utils-network

 # If the system is on an IPv6 network
 IPV6_NETWORK='2001:470:26:307'
 
-# Destinations used to get the external IP address of this system
-# Google ipv6 DNS is 2001:4860:4860::8888
+# Destinations used to get the local IP address of this system
+# Google ipv6 DNS   2001:4860:4860::8888
+# OpenDNS ipv6 DNS  2620:0:ccc::2
 IPV4_ADDRESS_TEST_DESTINATION='85.214.73.63'
 IPV6_ADDRESS_TEST_DESTINATION='2620:0:ccc::2'
-
+EXTERNAL_IP_LOOKUP_URL='ifcfg.me'
 
 # The static IP address of the system within the local network
 # By default the IP address is dynamic within your LAN
     mark_completed $FUNCNAME
 }
 
+function get_external_ipv4_address {
+    nslookup . $EXTERNAL_IP_LOOKUP_URL | grep Address | tail -n 1 | awk -F ' ' '{print $2}'
+}
+
 function get_ipv4_address {
     IPv4dev=$(ip route get $IPV4_ADDRESS_TEST_DESTINATION | awk '{for(i=1;i<=NF;i++)if($i~/dev/)print $(i+1)}')
     echo $(ip -o -f inet addr show dev "$IPv4dev" | awk '{print $4}' | awk 'END {print}' | awk -F '/' '{print $1}')