should `add-to-ordered-list' be able to use tests other than `eq'?

[Drew Adams]

`add-to-list' uses `equal'.  Why does `add-to-ordered-list' use `eq'?

And if this `eq' behavior will be kept, then the NEWS (NEWS.22) is incomplete
(misleading) regarding the introduction of this function.  It says:

 *** New function `add-to-ordered-list' is like `add-to-list' but
 associates a numeric ordering of each element added to the list.

"Like" is pretty vague here.  It is not "like" `add-to-list' in the way it tests
membership etc., unless you consider `eq' to be "like" `equal'.

This is the (3-message) thread that discussed adding this function:
http://lists.gnu.org/archive/html/emacs-devel/2005-06/msg00835.html

Should `equal' be used instead of `eq'?  Of if `eq' is the best default, should
the function accept an optional TEST arg?

For symbols (the originally proposed use case) there is no difference, but for
arbitrary Lisp objects there can be a big difference between `eq' and `equal'.