* develop-ascraeus:
[ticket/11148] Remove unneeded variable mimetype and use type octet-stream
[ticket/11148] Change expected output with disallowed content in test
[ticket/11148] Always use the output of the mimetype guesser in get_mimetype
[ticket/11148] Get rid of extra line in mimetype guesser setter doc block
[ticket/11148] Add missing parts to docblock of get_mimetype() method
[ticket/11148] Default to application/octet-stream if no mimetype given
[ticket/11148] Use mimetype guesser for uploaded avatars
[ticket/11148] Pass mimetype guesser to upload_attachment() function
[ticket/11148] Add mimetype guesser to filespec and fileupload class