reverting to `...` in config.*

[Karl Berry]

Dmitry - I've received another bug report from a Solaris 10 user about
config.guess breaking because of using $(...).

I implore you to revert to good old `...`. As far as I can see, config.*
should be maximally portable, since after all their purpose is to
identify systems, and that means using `...`, not $(). There is, so far
as the previous discussion turned up, no technical gain, only loss.

It seems crazily wrong for every package that uses config.* to suddenly
have to go look for a shell that supports $() just to run the config
scripts on old-enough systems.  config.* is used far more widely than
just autoconf.

Thanks for considering. --karl