iptables: bump dependency on libnftnl to >= 1.1.3

New iptables release requires a newer libnftnl version.
Signed-off-by: Arturo Borrero Gonzalez <arturo@debian.org>

debian/control

@@ -13,7 +13,7 @@ Build-Depends: autoconf,
                libnetfilter-conntrack-dev,
                libnetfilter-conntrack3,
                libnfnetlink-dev,
-               libnftnl-dev,
+               libnftnl-dev (>= 1.1.3),
                libtool (>= 2.2.6)
 Standards-Version: 4.3.0
 Homepage: http://www.netfilter.org/