RFC: Top level configure: Require a minimum version 6.8 texinfo

[Tom Tromey]

>>>>> "Nick" == Nick Clifton via Gdb-patches <gdb-patches@sourceware.org> writes:

Nick>   The reason for the change is that the bfd documentation now needs at
Nick>   least version 6.8 in order to build[1][2].

Sorry about this.  It was fallout from my patch.

However, GDB has used this same one-argument @node syntax for a long
time without any complaint.  Like, python.texi has used this since at
least 2014.

So, if makeinfo 6.8 is really needed by BFD, then I think it must be for
some other reason.

Tom