[v3] possible backwards include removal

[Benjamin Kosnik]

> Of course, I agree with the idea, in principle. But why we are keeping
> only *part* of the headers?

These are the headers that look the weakest to me. They are mostly old HP includes.

> I think this is confusing. I vote for either removing everything or
> nothing: and the possible rationale for the former option are exactly
> those two that you mentioned above.

We have to keep some of them. I'd like to remove the rest, because they
are just cruft, because I think nobody uses them, and party to see if
anybody cares before we do more dramatic surgery, as you suggest, next
year.

-benjamin