convert-ly on translations

[Graham Percival]

I'm still working on a general policy proposal for convert-ly, so
don't get side-tracked with that.

Translators: as a one-time thing, could you run convert-ly on your
Documentation/??/ files?  Please check
- each file should have a @c version.  (convert-ly will complain if it
doesn't find one)
- any "not smart" warnings should be addressed; as always, look at the
English docs for the correct lilypond input code.

Cheers,
- Graham