bug#7118: 24.0.50; dired-subdir-alist, dired-directory, etc.: necessarily buffer-local

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

We should use `make-variable-buffer-local' with vars such as
`dired-subdir-alist' and `dired-directory', instead of just calling
`make-local-variable'.  Why?  Because these vars MUST be buffer local,
and we might as well make the code clearer by pointing that out.  That
is precisely the use case for `make-variable-buffer-local': a var that
is necessarily buffer-local.
 
Also, the doc strings are otherwise incomplete/vague: for
`dired-subdir-alist', for example, it speaks of "the buffer".  The var's
value is local to each particular Dired buffer, and this needs to be
made more clear.  If we use `make-variable-buffer-local' that will add
the necessary info to `C-h v' so that the doc strings begin to make
sense.  (Still, we should mention in the doc string of
`dired-subdir-alist' that the subdirs are subdirs of `dired-directory'.)
 

In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2010-09-20 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4) --no-opt --cflags
-Ic:/imagesupport/include'