Files with right-to-left override in filename should be marked dangerous

[dputtick]

https://krebsonsecurity.com/2011/09/right-to-left-override-aids-email-attacks/
https://blog.malwarebytes.com/cybercrime/2014/01/the-rtlo-method/

As mentioned in CIRCL/Circlean#52, PyCIRCLean should strip out RTL (&rlm / u"\u202E") characters when copying to the destination directory. Also, files like this should be marked as dangerous, as there is no good reason to find a RTL character in a filename.