bug#10908: 24.0.94; doc of `prefix-numeric-value'

[Drew Adams]

Not sure whether you'll see this as a bug.  It's one of those things
that is unspecified.  Whether that's a good thing or not, you decide.
 
The reason this came up is that a user was doing M-: (foo-mode t)
instead of M-: (foo-mode 1).  It turns out that (prefix-numeric-value t),
which comes here from the `define-minor-mode' code, does evaluate to 1.
 
But that fact is not stated anywhere in the doc (manual or doc string),
AFAICT.  Instead, what's said is that `prefix-numeric-value' accepts a
raw prefix arg as argument and gives you the numeric prefix-arg value
that corresponds to it.  The argument must supposedly be "a valid raw
prefix argument value".
 
And the doc for "raw prefix arg" is pretty clear that it can never be
something like `t'.
 
The question is, should we say what `prefix-numeric-value' returns for
an arg that is not a raw prefix argument?
 

In GNU Emacs 24.0.94.1 (i386-mingw-nt5.1.2600)
 of 2012-02-26 on MARVIN
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.6) --no-opt --enable-checking --cflags
 -ID:/devel/emacs/libs/libXpm-3.5.8/include
 -ID:/devel/emacs/libs/libXpm-3.5.8/src
 -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
 -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
 -ID:/devel/emacs/libs/giflib-4.1.4-1/include
 -ID:/devel/emacs/libs/jpeg-6b-4/include
 -ID:/devel/emacs/libs/tiff-3.8.2-1/include
 -ID:/devel/emacs/libs/gnutls-3.0.9/include'