file(1) and marshal(1) assign vCards a MIME type of text/x-vcard.
This patch changes them to use the IANA assigned type 'text/directory'.

Note that with this patch, "file -m vcard-file" will print the string

	text/directory;profile=vcard

I.e. it includes the recommended 'profile' parameter. This
could potentially break existing code that naïvely parses
the output by assuming everything after the '/' is the
subtype. But considering how this output is typically used it
shouldn't be an issue.