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

[martin rudalics <rudalics@gmx.at>]

 > Would it be ok to just work around this by giving the
 > help-for-help buffer a title that is not "*Help*"? Most uses of
 > special-display-buffer-names aren't going to cause this problem.

`help-for-help' pops up the *Help* buffer in a separate frame.  Typing a
character now may cause its window display something else.  Thereafter,
`help-for-help', recalling that it popped up a frame and wrongly
assuming that the user has finished viewing its buffer, decides to
iconify the frame.

So giving the `help-for-help' buffer another name ("title") should
indeed fix this and I initially thought to go that way.  But, on the
other hand, we usually _want_ to reuse that frame for displaying other
help instead of having to deal with two separate help-related frames.

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'.

martin