New obsolete.el file for obsolete stuff?

[Stefan Kangas <stefan@marxist.se>]

I was investigating some XEmacs compat code the other day and stumbled
across their library obsolete.el, which they used to put all their
obsolete aliases.

You can find their library here:

    https://bitbucket.org/xemacs/xemacs/src/default/lisp/obsolete.el

Its Commentary says:

    The obsoleteness support used to be scattered throughout various
    source files.  We put the stuff in one place to remove the junkiness
    from other source files and to facilitate creating/updating things
    like sysdep.el.

I think this is a nice idea to basically move some cruft out of the way,
to where we don't need to see it.

Could we do something similar for Emacs?  I'm thinking that we don't
need to move all stuff at once, but if we create the file with a basic
structure, we could start using it little by little.

Best regards,
Stefan Kangas