MAZE THING

I fancied making something nice and a bit graphical, decided on a maze
generator/solver as it seemed fun and chill.  The build is handled
with CMake:

	cmake -B build       # Configure build
	cmake --build build  # Build
	build/maze-thing     # Run

I use Clang but the code is ISO C11 so it should work with other
compilers.  Dependency-wise, it should only need the Xlib libraries
and headers.