libctf: update regexp to allow makeinfo to build document

libctf: update regexp to allow makeinfo to build document

While trying to build gdb on latest openSUSE Tumbleweed, I noticed the
following warning,

 checking for makeinfo... makeinfo --split-size=5000000
 configure: WARNING:
 *** Makeinfo is too old. Info documentation will not be built.

then I checked the version of makeinfo, it said,
======
$ makeinfo --version
texi2any (GNU texinfo) 7.0.1

Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
======

After digging a little bit, it became quite obvious that a dot is
missing in regexp that makes it impossible to match versions higher than
7.0, and here's the solution:

-       | egrep 'texinfo[^0-9]*(6\.[3-9]|[7-9][0-9])' >/dev/null 2>&1; then
+       | egrep 'texinfo[^0-9]*(6\.[3-9]|[7-9]\.[0-9])' >/dev/null 2>&1; then

However, Eli pointed out that the solution above has another problem: it
will stop working when Texinfo 10.1 will be released.  Meanwhile, he
suggested to solve this problem permanently.  That is, we don't care
about the minor version for Texinfo > 6.9, we only care about the major
version.

In this way, the problem will be resolved permanently, thanks to Eli.

libctf/ChangeLog:

	* configure: Regenerated.
	* configure.ac: Update regexp to match versions higher than 7.0.