Requesting review of PR 289 to the autoconf-archive GitHub repo

Hi, pinging this PR on GitHub doesn't seem to have gotten a response
recently, so I figured I'd try pinging it via this mailing list next:
https://github.com/autoconf-archive/autoconf-archive/pull/289
I get that it's kind of big and intimidating with all the changed
files in it, but I think overall it ought to be worthwhile for a
number of reasons:
- the combination of the use of autoupdate with manual verification
ensures that the included autoconf macros are up-to-date with modern
autoconf standards for style, quoting, and general current usage
practices
- the addition of (the beginnings of) a testsuite ensure that all the
included macros are parseable, and is a step towards having some sort
of verification that they're all valid
- changes to the bootstrap script make it now pass shellcheck, and
improve its resilience and informativeness

Thanks,
Eric Gallager