Small backward compatibility to buckets that were managed with original s3fs

There was a problem for people using the regular s3fs and now changed to s3fs-c.
I use the the term directory a bit loosely here :)

When accessing a file directly (e.g. stat /mnt/s3fs/some/nested/file/in/a/path.jpg), it didn't find the file because when stat was nesting through the directories it received that "some" is not a directory. On S3 "some" was a key with application/x-directory generated by the original s3fs and it also was a directory.

In more depth, when s3fs-c queried getattr, it didn't check for application/x-directory on keys, so it set the mode as a regular file, even though there was a directory behind it. (and caching prevented readdir to update the stat).

This pull request basically adds this backward compatibility feature (dc2559ba4cc1ebe15b6c99ce4f8d46d9f90a85ec), as 'c' stands for compatibility, at least when reading. :)
Plus, merging the bump to 1.61 from memorycraft/s3fs-cloudpack@a5e4da332d51bf6409541ae041ef725e591b0963