[RFC] Add missing copyrights

[Roland McGrath]

> Would you not agree that when it comes to issues of copyright
> and licensing that the rules we apply should have as few
> exceptions as possible? Therefore "Add copyright headers to everything"
> just seems like a win with no lose? What did I miss?

Fair enough.  But when we get to other exceptions, like things that need
special variants of the license text, then the notion that you are keeping
things simple and uniform breaks down.