[translations] x-ref intranslated docs

[Jean-Charles Malahieude <lilyfan@xxxxxxxxx>]

Hi John, and a bonne et heureuse année, avec un PHD !

Ther seem to be a problem with cross referencing to another splitted
manual, at least towards "usage".

I fully translated running.itely (part of usage), which contains
unnumbered sectioning.
I then translated input.itely (part of notation), where there is a link
to a node which is an unmberedsubsec in running (Invoking lilypond).

Big page links correctly, but it gives a 404 with all translated
versions of the split manual. I have to say it works with the English
version.

It appears that the English version mentions section and
unnumberedsbusec as anchor (l. 85):
<p>For more information on output formats, see <a
name="index-Invoking-lilypond"></a>
<a
href="../usage/command_002dline-usage.html#invoking-lilypond">Invoking
lilypond</a>.
</p>

on the contrary, not the translated version (e.g. French has on line 
102) the unreachable:
<p>Pour de plus amples informations quant au format des résultats,
consultez le chapitre <a name="index-Lancement-de-lilypond"></a>
<a href="../usage/invoking-lilypond.fr.html">Lancement de lilypond</a>.
</p>

This does not happen with linking to LM because there is NO unnumbered 
in it, and as soon as I "number" the sectioning, there is no longer any 404.
Same when I change
 href="../usage/invoking-lilypond.fr.html"
to
 href="../usage/command_002dline-usage.fr.html#invoking-lilypond"

Do you have a clue?

TIA
Jean-Charles