bug#5809: 23.1.94; cross-reference by anchor yields in accurate position

[Eli Zaretskii]

> From: Juri Linkov <juri@jurta.org>
> Cc: "'Eli Zaretskii'" <eliz@gnu.org>,  5809@debbugs.gnu.org
> Date: Mon, 05 Apr 2010 19:45:56 +0300
> 
> The ratio of 66 to 839 is 8%.  So you guess of 10% is closer to the
> actual percentage.

That's only one manual.  The Emacs manuals don't use @anchor very
much.  In the GDB manual, the ratio is 65 to 418 (15.5%), which is
twice the ratio we see in ELisp.