package--builtin-versions

[Artur Malabarba]

I stumbled into this odd little variable the other day, and I was
wondering why it's designed the way it is.

AFAIKT, the `package--builtin-versions' variable is only used by
`package.el', but it's defined in `subr.el', and it's populated in
`loaddefs.el' which is generated by `autoload.el'.
Is this for performance reasons?

I always assumed it was like this because of some complex
interdependency, but I've been grep'ing and I can't find this variable
being used anywhere outside package.el.
I'm wondering if this can be simplified to go entirely in package.el.
Something like:

  (defvar package--builtin-versions
    (eval-when-compile
      (go-thtough-builtin-packages-and-accumulate-autoloads)))

This should still happen at bootstrap time, so it wouldn't affect
Emacs startup. In fact, it might help emacs startup a little bit,
since there would be 76 fewer forms in `loaddefs.el'.

Cheers,