Fix style of FindExecInfo.cmake.

Make this file look more like a normal CMake find module.
Remove superfluous (and redundant) debug output.

We print this below; no need to print it here.
Actually use Transition::Dot()!

Somehow this code escaped de-duplication...
For now, concentrate on logical OR.

Implementing AND is a bit tricky: among other things, it makes our automata look a lot less like automata. We can get most of the way by just writing separate temporal assertions, so for now, let's focus on other things.
GC some unused code.