libxt_recent: add --mask netmask

This new option will be available in the Linux kernel 3.5

[ Pablo fixed coding-style issues and cleaned up this. Added
  manpages as well ]

Signed-off-by: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
3 files changed