- this is useful to safe one extra call when it is known that there
should be changes on the remote. In that case it will immediately
skip forward to calling device/get_changes
- since mediafire cannot deal with empty files, we put new files into a
temporary location and upload them once they get closed
- add create and write functions to fuse
- pass a file handle to mfconn_api_upload_simple instead of a path
- allow calc_sha256 to also compute the file size
- error out when the key returned by upload/simple is empty
- make valgrind.supp more lenient
