netlink: Allow to invert the ranges

netlink: Allow to invert the ranges

This patch fix the bug:

http://bugzilla.netfilter.org/show_bug.cgi?id=924

Before, nftables doesn't permit invert ranges. This patch allows
add rules like this:

nft add rule ip test input ip daddr != 192.168.1.2-192.168.1.55
or
nft add rule ip test input ip daddr == 192.168.1.2-192.168.1.55

Also, we still have the option for adding rules like this:

sudo nft add rule ip test output frag id 33-45

Signed-off-by: Alvaro Neira Ayuso <alvaroneay@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>