Remove autogenerated files and rely on autoreconf only

[michael-o]

Unfortunately, this requires GNU Autoconf 2.70: https://lists.gnu.org/archive/html/autotools-announce/2020-12/msg00001.html

2020-10-20 Zack Weinberg [email protected]

Improve handling of missing aux scripts (autoreconf)
Make ‘autoreconf --install’ add config.sub, config.guess, and
install-sh to the source tree when necessary. This is only relevant
for packages that don’t use Automake, because ‘automake --add-missing’
already adds these scripts to the source tree, but apparently there
are plenty of packages out there that don’t use Automake, didn’t need
config.{sub,guess} with autoconf 2.69, and do need them with 2.70.
Such packages will need to have their equivalent of ‘make dist’
manually updated to ship the new files, of course.

This will only affect those who are developing, those who use a source tarball will use the src distro which expects autoreconf -fi to be run beforehand.

Note: Autoconf 2.70 has been around for 3,5 years...

[michael-o]

If I don't here any objections I will merge this by end of week.