New sftp(1) regression tests

I've developed some new regression tests for sftp(1), covering the following functionality:

• get/put -r (recursive transfers)
• get/put -p (preserving files' atime and mtime)
• chown
• chgrp
• chmod

If you'd like to integrate them into your OpenBSD -CURRENT tree, you can download the diff here.

If you have any suggestions, just let me know in the comments!