bug#20815: 25.0.50; doc of `null'

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

BTW, the URL for the online manual is not good for this node.

Following the convention, it should be simply
http://www.gnu.org/software/emacs/manual/html_node/elisp/List-related-Predicates.html

But it is instead:
http://www.gnu.org/software/emacs/manual/html_node/elisp/List_002drelated-Predicates.html

Somehow, the hyphen got translated to `_002d', unhelpfully.

It is good to follow a consistent convention.  I take advantage
of that, for example, in this command, which I use several times
a day to point Web readers to the manual (e.g. from stackoverflow
and emacs.stackexchange.com):

(defun Info-goto-node-web (node &optional flip-new-win)
  "Use `browse-url' to go to Info node NODE using a Web browser.
With a prefix arg, reverse the effect of option
option`browse-url-new-window-flag'.

NODE is the name of a node in the GNU Emacs or Elisp manual.
Alternatively, NODE can have the form (MANUAL)NODE, where MANUAL is
\"emacs\" or \"elisp\" and NODE is the name of the node in that
manual.  Empty NODE in (MANUAL) defaults to the `Top' node."
  (interactive
   (list (Info-read-node-name "Go to node: " Info-current-node)
         current-prefix-arg))
  (require 'browse-url)
  (unless Info-current-file (error "This command must be invoked from Info"))
  (browse-url (Info-url-for-node node)
              (list (if flip-new-win
                        (not browse-url-new-window-flag)
                      browse-url-new-window-flag))))

`Info-url-for-node' returns "a URL for NODE, a node in the GNU
Emacs or Elisp manual."  It does this:
(replace-regexp-in-string "[ \t]+" "-" node t t).  That doesn't
DTRT for the node reported in this bug report, for example.