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

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

It seems that whenever users ask a function-advising question anywhere,
Stefan lets them know that `defadvice' is nearly deprecated and not
really being bug-fixed or developed further.  He advises ;-) them to use
the `nadvice.el' features (e.g., `add-function') instead.

Wunderbar.  But meanwhile, there is nothing in the manual about any of
the new stuff.  Still, users are being discouraged from using `defadvice'.
This is not right.  The new advice functionality should be fully
documented, and that should be done before advising people here and
there to use the new and abandon the old.

This bug report is to ask for full doc of `nadvice.el' features in the
Elisp manual in the Emacs 24.4 release.

In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2014-01-01 on ODIEONE
Bzr revision: 115827 eggert@cs.ucla.edu-20140101192741-bi5hb4xb4kdi2zpw
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/binary --enable-checking=yes,glyphs
 'CFLAGS=-O0 -g3' LDFLAGS=-Lc:/Devel/emacs/lib
 CPPFLAGS=-Ic:/Devel/emacs/include'