bug#15239: 24.3.50; doc string of `fringe-styles'

[Drew Adams]

Unless I'm missing something, this doc string seems wrong on several
counts.  And it is important because it is referred to by the doc of
various fringe functions and variables, including `fringe-mode' itself.

1. The doc says that an alist element "has the form (NAME . WIDTH),
   where NAME is a mnemonic fringe mode name (a symbol)".

   Wrong.  NAME is *NOT* a symbol.  Presumably this wants instead to say
   that NAME is a symbol name.  But why it would want to say that here
   is not clear anyway.

2. The doc says that "WIDTH is one of the following:" followed by this:

   "a cons cell (LEFT . RIGHT), where LEFT and RIGHT are respectively
    the left and right fringe widths in pixels, or nil (meaning to
    disable that fringe)."

   Wrong again.  `nil' for LEFT or RIGHT does *NOT* mean to "disable
   that fringe".  It means to "use the default width (8 pixels)", the
   same thing `nil' means as a non-cons value for WIDTH, but in this
   case only for "that fringe".

Again, unless I'm missing something.

In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-08-23 on ODIEONE
Bzr revision: 113986 rgm@gnu.org-20130823185841-zoy6h1qk433ibrlf
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'