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

[Drew Adams]

> > 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.

Agreed on both counts.