ddns-scripts: send_update() detection private IPv4

correction of excluding private IPv4 in file dynamic_dns_functions.sh in function send_update().
Now correct detection of 172.16. - 172.31. and only 192.168.
increment PKG_RELEASE in Makefile to reflect changes.

Signed-off-by: Christian Schoenebeck <christian.schoenebeck@gmail.com>