ipfw(8): Fix a few mandoc related issues
- no blank before trailing delimiter
- missing section argument: Xr inet_pton
- skipping paragraph macro: Pp before Ss
- unusual Xr order: syslogd after sysrc
- tab in filled text
There were a few multiline NAT examples which used the .Dl macro with
tabs. I converted them to .Bd, which is a more suitable macro for that case.
MFC after: 1 week