Sys::Syslog is missing IPv6 support

[jschauma]

Looks like Sys::Syslog can only log over IPv4.

This is due to the use of AF_INET explicitly here:
https://github.com/maddingue/Sys-Syslog/blob/master/Syslog.pm#L687

and here:
https://github.com/maddingue/Sys-Syslog/blob/master/Syslog.pm#L727

and related inet_aton calls. It would be nice to add support for IPv6 syslogging.