bug#35536: 27.0.50; Expose buffer's marker list to Elisp

[Stefan Monnier]

> Whether or not one should be able to depend on such
> an order is a separate question.

I'm fine with a `markers-in` which returns markers in the order found in
the C code.  But the docstring should state clearly that you can't rely
on this ordering.

I expect many uses won't care about the ordering anyway, so we don't
need to bother `sort`ing, although the performance cost of `sort`ing will
likely always be negligible.


        Stefan