bug#14120: invalid load-history in emacsen that CANNOT_DUMP

[BT Templeton]

"loadup.el" sets `current-load-list' to nil, apparently so that it will
have that value when restarting a dumped emacs. However, when Emacs is
built with CANNOT_DUMP defined, "loadup.el" evaluates `top-level'
instead of dumping. This can lead to invalid entries in `load-history'
if something is defined, required, etc. during evaluation of that form.

For example, load-history will contain `((require . tetris))' if
~/.emacs defines this hook:

(add-hook 'lisp-interaction-mode-hook
          (lambda () (require 'tetris)))

For `require', the problem can be fixed by also setting
`load-in-progress' to nil in "loadup.el", but this doesn't fix the bug
for other functions that change the load history.

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