Fix incorrect naming for MacRoman encoding

MacRoman encoding uses the word "macintosh" as its primary identifier as defined by the IANA. See http://en.wikipedia.org/wiki/Mac_OS_Roman for more info.

This fixes problems when using iconv to convert MacRoman encoding to other encodings on unix OS (and perhaps other OS types).

Signed-off-by: Dries Vints <dries.vints@gmail.com>