crunch: other way to detect if a path is a file or a directory

[illwieckz]

readdir() doesn't support file detection on all file systems, so we use stat() as a fallback.

This makes the crunch tool works with files stored over the network on NFS shares on MacOS.

We also report if the current code fails to detect if a path is a file or a directory, just in case some other corner case surfaces.

It fixes:

• Crunch fails to open files on NFS and SSHFS network file systems #37

[illwieckz]

This looks good enough for me and it works well.

It would be possible to make the code smaller by relying on stat in all cases, but I assume that only calling stat when readdir doesn't provide the required data means we don't do extra IO with stat when readdir is enough (readdir being called for other things in all cases anyway).

When the Filesystem implementation is complete, readdir will only be used, while the code works on less implemented filesystems with an extra stat call.