Add some random improvements

I have selected these commits for the future work on py3k, and I don't see any reason why not to merge them, although I don't see any particular reason why to do so. Just cleanup.

Rand.py is just expansion into proper Python functions so we can add proper documentation strings.

The second commit relates to the support of Twisted by M2Crypto. It was broken for long time and then during some bit heated discussion with Twisted maintainers (where they expressed doubts whether they care for M2Crypto support at all, because for some more simple uses they have their own SSL support), somebody just went and fixed that module so it works with the current Twisted and with Python 3k. I am still ambivalent whether we really need this module in M2Crypto at all, but removing it would violate API and when it is already working, we just use it, I guess.