IPv6 support for greylist and blackhole

[foscarini]

Hello Sean

I have made a lot of changes in tumgreyspf, mainly to support IPv6 in the greylisting and blackhole checks.

I also updated tumgrey-stat and tumgrey-clean, to deal with the IPv6 files and directories, and to cleanup all the expired files, doesn't matter if the greylist check is IP only, or IP + recipient.

I know that the changes are extensive, and I probably changes one or two things that I shouldn't, but I am deploying an new IPv6 mail MX, and I want to continue using tumgreyspf.

The code was tested in Ubuntu 15.10, with python 2.7.10 installed via APT.