[describe what autoconf is, where one gets it, and why one would need it]
"Autoconf is an extensible package of m4 macros that produce shell scripts to automatically configure software source code packages," according to its official home page [L1 ].
autoconf acts on configure.in to generate configure.
drh describes "Using Autoconf With Mktclapp" [L2 ].
"Stop the autoconf insanity! Why we need a new build system." [L3 ]
[Refer to TIP 34?]