text on tool-bar-lines could use clarification

[Drew Adams]

Emacs-Lisp manual:

node Window Frame Parameters:

  `tool-bar-lines'
     The number of lines to use for the tool bar.  A value of `nil'
     means don't display a tool bar.  (GTK allows at most one tool bar
     line; it treats larger values as 1.)

node Tool Bar:

  "The frame parameter `tool-bar-lines' (X resource `toolBar') controls
  how many lines' worth of height to reserve for the tool bar.  A zero
  value suppresses the tool bar.  If the value is nonzero, and
  `auto-resize-tool-bars' is non-`nil', the tool bar expands and
  contracts automatically as needed to hold the specified contents."

The text in node Tool Bar should perhaps be clarified wrt the value nil. Nil
suppresses the tool bar, whereas this text implies something different
(since nil != 0).

Similarly, the text in node Window Frame Parameters should perhaps point out
that a value of zero has the same effect as nil.

BTW - Why do we allow both 0 and nil to have the same effect? Is there some
advantage to doing this?

In GNU Emacs 22.0.50.1 (i386-mingw-nt5.1.2600)
 of 2005-06-26 on NONIQPC
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc
(3.3) --cflags -I../../jpeg-6b-3/include -I../../libpng-1.2.8/include -I../.
./tiff-3.6.1-2/include -I../../xpm-nox-4.2.0/include -I../../zlib-1.2.2/incl
ude'