bug#20825: 25.0.50; Cannot view info docs anymore (100% CPU)

[Eli Zaretskii]

> From: Tassilo Horn <tsdh@gnu.org>
> Date: Tue, 16 Jun 2015 09:06:55 +0200
> 
> With emacs HEAD e80225000dda3f1deac5ea95a9253301b05fbed7, emacs starts
> using up 100% CPU time when trying to view some info documentation.
> 
>   1. emacs -Q
>   2. C-h i
>      The info index is shown properly
>   3. m emacs RET
> 
> Now emacs starts using up 100% CPU, and the emacs info docs aren't
> shown.  With `debug-on-quit' I obtain the following backtrace during the
> hang.
> 
> Debugger entered--Lisp error: (quit)
>   count-lines(1 1)
>   line-number-at-pos(70)
>   filepos-to-bufferpos(1116 approximate)
>   Info-find-node-2("/home/horn/Repos/el/emacs/info/emacs" "Top" nil nil)
>   Info-find-node("emacs" "Top" nil nil)
>   Info-goto-node("(emacs)" nil)
>   Info-menu("Emacs" nil)
>   funcall-interactively(Info-menu "Emacs" nil)
>   call-interactively(Info-menu nil nil)
>   command-execute(Info-menu)

Fixed.