Obsoleting end-user-functions [was: turn-on-* type functions]

[Stephen J. Turnbull]

Stefan Monnier writes:

 > [C]urrently we don't have any good way to obsolete end-user-functions,
 > since the obsolescence-info is only used by the byte-compiler

Two easy, non-invasive ideas:

(1) Have help functions such as describe-function present the o-info
    (and maybe apropos could have a very abbreviated notation)

(2) Provide a help-obsolete (maybe apropos-obsolete is a better name?)
    function which lists all symbols with o-info in apropos style.

 > which the end-user is likely to never run on his .emacs).

A harder, invasive idea: get rid of explicit byte-compilation, by
default.  If Emacs always byte-compiles out-of-date libraries at load
time, the warnings would be generated.

Rationale: I don't think I've ever seen a test-suite difference
between byte-compiled and directly interpreted code in XEmacs, and
only a few such bugs in beta testing or end use.  Of course in the
nature of Lisp there may need to be a way to inhibit byte compilation,
but these days I think it's appropriate to require a flag of some kind
(command-line option, Lisp variable) to inhibit.