insert-string

[Richard Stallman]

I see one clear problem with this patch: insert-string must continue
to do what it does now.  User Lisp code surely uses it, and possibly
with non-string arguments.  Making it equivalent to insert is sure to
cause problems.  So please reimplement it with the same old
functionality.  An implementation in Lisp would be fine.

We may find that some of the other functions in mlsupport are
sometimes used.  If so, we will want to add the specific functions
back, perhaps in subr.el.