[Maxima-discuss] Bump Texinfo version requirement to 6.0 (was 5.1) for Maxima build

[Robert D. <rob...@gm...>]

I'm going to bump the Texinfo version requirement from 5.1 to 6.0 in
configure.ac.

The @sub command (subscript) is used in one of the Texinfo files
(format.texi) and although it's possible to work around the lack of
@sub by using some other command, I think it is preferable in this
case to just use a somewhat more recent Texinfo installation.

Texinfo 6.0 was released in 2015 so I think this is not a burdensome
requirement. For the record, Texinfo 5.1 dates to 2013.

FWIW and all the best.

Robert