bug#5274: 23.1; doc string of ad-add-advice

[Drew Adams]

Doc string:
 
"Add a piece of ADVICE to FUNCTION's list of advices in CLASS.
If FUNCTION already has one or more pieces of advice of the specified
CLASS then POSITION determines where the new piece will go.  The value
of POSITION can either be `first', `last' or a number where 0 corresponds
to `first'.  Numbers outside the range will be mapped to the closest
extreme position.  If there was already a piece of ADVICE with the same
name, then the position argument will be ignored and the old advice
will be overwritten with the new one.
    If the FUNCTION was not advised already, then its advice info will be
initialized.  Redefining a piece of advice whose name is part of the cache-id
will clear the cache."
 
None of the parameters, except POSITION, are described. OK, one can
guess that FUNCTION is a function (but `functionp' or `fboundp'?), but
there is no indication what ADVICE, CLASS, and POSITION are - what
forms they can take.  Might as well say "a piece of FOO" and "list of
foos in THROMBIT".

Each of these parameters needs to be described, just as we do for any
other function's parameters.
 

In GNU Emacs 23.1.1 (i386-mingw-nt5.1.2600)
 of 2009-07-29 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4)'