bug#16402: 24.3.50; Document nadvice.el stuff in Elisp manual before Emacs 24.4

[Daniel Colascione]

On 01/10/2014 07:15 AM, Drew Adams wrote:
> > > A rationale to explain why the existing advice package needs
> > > changing would also be helpful.
> >
> > Here are some of the reasons:
>
> Excellent.  Very glad to see design rationale documented like this.
> Seriously.  (Please keep it up.)

Agreed. nadvice sounds like a good implementation change. The advice 
*interface*, however, isn't going away, so I'm hesitant to recommend the 
nadvice interface as well. Users will be confused about which to use. 
(Yes, we can tell users that advice is deprecated, but then a very large 
amount of working elisp code users see is "deprecated". What message 
does that send?)

There's one part where I'm not sure I agree though.

>>  - advice.el is much too large to be preloaded,
>> so for example debug.el refrained from using it.

So what if it's large? Isn't it *because* a commonly-used package is 
large that we want to preload it? This way, we pay up-front for the cost 
of loading that package instead of making users load it on each start.