RFC: Moving C to its own directory

[Benjamin Kosnik]

> Can't we just have directories c/ objc/ cp/ java/ etc?
> I don't quite see what the extra fe/ level buys us.

Remember at the gcc summit where you were asking about interfaces between
the front ends and the back ends? (ie, what interface?). I see this
attempt at a coherent organization of the gcc sources as a first step at
attempting formal interfaces.

Perhaps I'm being optimistic. I think it's worth a shot though.

-benjamin