Implemented rrdbot with IPv6 support

[Stef Walter]

Attached is a pre-release build of rrdbot with IPv6 support.

I haven't been able to fully test this feature, as although I have
configured IPv6 on my network, I haven't been successful in setting up a
SNMP agent that listens on IPv6.

Harry, I'm leaving this in your hands to test. I'd like to release the
next version of rrdbot within one week if possible. Let me know how it
goes.

You can use the attached pre-release build, or get the latest source
from git:

git clone git://memberwebs.com/rrdbot.git

Thanks in advance for your help.

Cheers,

Stef