bug#8869: Unjustified selection time-out

[Chong Yidong]

Glenn Morris <rgm@gnu.org> writes:

> 1) 20 seconds seems a very long default. If whatever Emacs wants to
> contact does not respond in say 5 seconds, is it likely to in 20?
>
> 2) Someone who starts Emacs from a menu item as opposed to a terminal
> probably won't see the message about x-select-enable-clipboard-manager.
> Could you not print "Attempting to contact clipboard manager..."
> in Emacs before it starts doing whatever it does?
>
> 4) The CLIPBOARD_MANAGER arg of x-selection-exists-p isn't documented.

I've fixed these in trunk.  Thanks.