bug#21327: [PATCH] Use @sub and @sup in documentation

[Eli Zaretskii]

> Date: Sun, 23 Aug 2015 18:51:33 +0800
> From: Xue Fuqiao <xfq.free@gmail.com>
> 
> Use @sub and @sup instead of [0-9]+\^[0-9]+ or [0-9]+\*\*[0-9]+ for
> inserting subscripts and superscripts in *.texi files.

Thanks, but I don't think we can accept this as written.  These two
commands were introduced in Texinfo 6.0, released only 2 months ago.
We cannot possibly unsupport all the previous versions of Texinfo, in
effect preventing anyone with an older version from building the docs,
it would be to draconian to our users.

If you really think this is such an important feature to have, at the
very least condition its use by @ifset and let the interested users
specify the appropriate -DFOO switch to makeinfo.