io.directories.search: Add two tests for find-up-to-directory, one that finds a file and one that doesn't.
io.directories.search: Add two tests for find-up-to-directory, one that finds a file and one that doesn't.

AlexIljin/factor,bpollack/factor,dch/factor,AlexIljin/factor,slavapestov/factor,AlexIljin/factor,tgunr/factor,dch/factor,bpollack/factor,dch/factor,mrjbq7/factor,tgunr/factor,factor/factor,slavapestov/factor,bjourne/factor,factor/factor,bjourne/factor,bjourne/factor,mrjbq7/factor,factor/factor,bjourne/factor,bpollack/factor,AlexIljin/factor,dch/factor,slavapestov/factor,tgunr/factor,tgunr/factor,tgunr/factor,nicolas-p/factor,nicolas-p/factor,nicolas-p/factor,nicolas-p/factor,factor/factor,mrjbq7/factor,nicolas-p/factor,bjourne/factor,tgunr/factor,AlexIljin/factor,slavapestov/factor,bpollack/factor,factor/factor,nicolas-p/factor,bjourne/factor,slavapestov/factor,mrjbq7/factor,bjourne/factor,slavapestov/factor,AlexIljin/factor,mrjbq7/factor,dch/factor,nicolas-p/factor,mrjbq7/factor,AlexIljin/factor,bpollack/factor,dch/factor,bpollack/factor,slavapestov/factor,bpollack/factor,factor/factor