@neologist,
You're spreading bullshit. Constantine did not "officially" do anything about Christianity, he simply took a pragmatic step to end controversy among his Christian subjects, who were, by the 4th century, a significant part of the population of the eastern portion of the empire. The first ecumenical council was convened at Nicaea, under his auspices, after he had been petitioned by bishops to do something.
Christianity
did not become the state religion of the Empire in Constantine's reign. There is also no evidence that he became a Christian himself, although is wife and his mother-in-law were Christians. Christian-biased scholars who want to avoid embarrassment generally allege that he made a death-bed conversion. Stories like that are convenient because they can't be checked, and the subject isn't leaving any documentary evidence after the event.
Of course, you can always go to Wikipedia to dispute my claim-- the article on Christianity becoming the state religions of the empire, and Constantine's alleged conversion was just vandalized on today's date. Eusebius, one of the most widely respected and accomplished liars in the history of historians, is the source of the story that Constantine saw a vision of the Christ before battle, with an inscription
In hoc signo vinces ("with this sign you will conquer") emlazoned in the sky. No such story circulated through Roman sources of the time, which would be remarkable if Constantine actually had such a vision and attributed his crucial victory to Jeebus. The only documentary evidence for the establishment of Christianity in the Empire is in the reign of his son, Constans, in the last decade of the fourth century.
