I guess assoc-delete-all should be announced in NEWS too?  Although it
looks like it could be replaced with cl-delete instead.

> Another thing is that the defcustom default value trick doesn't work as
> intended (as far as I understand the intention, at least).
>
>     ;; For backward compatibility check if short y/n answers are preferred.
>     (defcustom read-answer-short (eq (symbol-function 'yes-or-no-p) 'y-or-n-p)
>       "If non-nil, accept short answers to the question."

> I think we'd want some `auto' setting which would tell read-answer to
> look at the yes-or-no-p function value at run time.

Here's a patch for that against master (I already included this into the
backported patch above).