bug#1322: dedicated *Help* and M-x help-for-help

[Geoff Gole]

> An easy solution is to use an extra variable, set by `help-for-help' and
> reset by `with-help-window', to control iconification.  But I never had
> the time to check whether all functions run by `help-for-help' also run
> `with-help-window'.

I'm not sure this will be sufficient. Remember that help-for-help
has entries that bring up info, NEWS, etc. Now if *Help*
is the only thing in special-display-buffer-names and
help-for-help is in it's own frame, accessing these help
functions through help-for-help is going to spawn another frame.

To see this:

  emacs -Q
  M-: (setq special-display-buffer-names '("*Help*"))
  f1 f1 C-a
  Return to first frame
  f1 f1 C-n

Now there's four frames open! Surely this is not the intended
behaviour of help-for-help, even after fixing the iconification
issue.

One way to work around that is to restrict help-for-help to the
original frame in some way. If that is not acceptable then
shouldn't we at least make sure that the user's commands are
taking effect in the correct frame? It doesn't seem right that a
help command will display differently when you run it through
help-for-help.