bug#57107: texinfo-format-buffer does not work in calc.texi

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Wed, 10 Aug 2022 03:18:33 -0700
> 
> Running `texinfo-format-buffer' in "doc/misc/calc.texi" leads to:
> 
>     Debugger entered--Lisp error: (error "Texinfo file needs an
> ‘@setfilename FILENAME’ line")
>       error("Texinfo file needs an `@setfilename FILENAME' line")
>       texinfo-format-buffer-1()
>       texinfo-format-buffer(nil)
>       funcall-interactively(texinfo-format-buffer nil)
>       command-execute(texinfo-format-buffer)
> 
> Of course, that file does have:
> 
>     @setfilename ../../info/calc.info

It's a bug in calc.texi: it violates the following requirement of
Texinfo:

  The '@setfilename' line specifies the name of the output file to be
  generated.  When present, it should be the first Texinfo command (that
  is, after '\input texinfo'). ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ^^^^^^^^^^^^^^^^^^^^^^^^^^