Rejuvenating Autoconf

Alas, yes, it is. The thing is that it's tribal knowledge and due to the way things interact, hard to document effectively (it comes back to our lack of guide-level documentation). One also has issues with projects being embeddable into others (alas, also a more common occurrence today) with assumptions about what the top-level project means and such.

> make uninstall

This is because CMake allows for arbitrary code during installation (`install(<CODE|SCRIPT>)`) which can easily escape `install_manifest.txt`'s view of things. I wish the "everything is via `install(<FILES|DIRECTORIES|TARGETS|EXPORT>)`" flag to indicate that `install_manifest.txt` is at least potentially trustworthy were easier to toggle though.