bug#21981: request: dired: require dired-x by default

[Drew Adams <drew.adams@oracle.com>]

Why make dired-x obsolete if you are not going to add all
of its features to dired.el?  That makes no sense.

If you're not going to add all of the features then keep
dired-x.el, for now - and until you do add all of its
features.

Why should you, today, decide what Dired users might want
to use from dired-x.el?  It's been around for decades.  Are
you going to guess what bits users use?  And why should you?

I was in favor of moving dired-x.el to dired.el until you
started talking about removing features.

Or rather, I was, and still am, in favor of loading
dired-x.el along with dired.el.  I'm also in favor of loading
dired-aux.el along with the other two.

Is this some kind of (misguided) optimization?  What's
the reason for this kind of filtering?  Just leave it
alone, please, if you can't stop yourselves from removing
features.