Re: master 391ff93f763 3/4: * doc/misc/calc.texi (Musical Notes): Fix build with Texinfo 4.13.

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Ruijie Yu <ruijie@netyu.xyz>, Eli Zaretskii <eliz@gnu.org>
> Date: Wed, 09 Aug 2023 13:55:32 +0800
> 
> > I presume you made this change because of a newly introduced
> > warning/error -- sorry if I have missed any relevant discussion.
> 
> Yes; the file fails to compile with the last C version of makeinfo,
> 4.13.

Then I guess we are getting to the point where makeinfo 4.13 will no
longer be a viable option.  The current makeinfo, though still slower
than 4.13, is significantly faster than the original 5.x versions if
you build Texinfo with Perl extensions, and has too many useful
features to stay with 4.13.  So I urge you to upgrade.

> > I don’t have any experience in writing texi files, but can we do this
> > instead without triggering any warnings/errors?
> >
> >     @slanted{C}@sub{@slanted{4}}
> 
> Unfortunately not, because Texinfo 4.13 does not support @sub at all.
> Eli, does a substitute for @sub that works in these old versions of
> Texinfo present itself to you?

I don't know, please ask on the Texinfo list.  And meanwhile please
revert those changes, they should not have been installed in the first
place.