iptables: use multipurpose binaries and bump version

Closes #587

- bump version to 1.4.4
- iptables-optional-ipv6.patch no longer needed (included in upstream)
- use ipXtables-multi binaries with symlinks to ipXtables, ipXtables-save,
  ipXtables-restore instead of 3 distinct binaries

Signed-off-by: Olaf Rempel <razzor@kopf-tisch.de>
Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>