Improve detection of application/mac-binhex40
The IANA type registration says that the file must begin with the string "(This file must be converted with BinHex 4.0)", but the binhex utility generates files that begin with "(This file must be converted; you knew that already.)".
https://www.iana.org/assignments/media-types/application/mac-binhex40 https://datatracker.ietf.org/doc/html/rfc1741 http://fileformats.archiveteam.org/wiki/Binhex https://github.com/VorpalBlade/macutils/blob/640782c6698a4d360711bbfb71a0d27dbd182d8f/binhex/dofile.c#L30