bug#36260: 27.0.50; isearchb should be reimplemented without iswitchb

[Stefan Kangas]

Richard Stallman <rms@gnu.org> writes:

>   > Yup; those are also solutions, but apparently the maintainers think that
>   > iswitchb isn't very useful anymore, but people still use isearchb,
>   > apparently.
>
> It seems that iswitchb is still useful for one thing: running isearchb.
> Thus, in fact it is not obsolete.
>
> I suggest de-obsoleting iswitchb, unless and until someone
> fixes isearchb not to use it any more.

We can just leave iswitchb as obsolete until isearchb is re-implemented
to not need it.  Even if we have to wait for a very long time for that
to happen, it costs us little, and will discourage anyone from building
new functionality on top of iswitchb.

IOW, there is no need to delete it "now" just because we said that we
will delete it "at some point".  We can just postpone its deletion.
That's what we already do with fastlock.el and lazylock.el.