Fix incorrect naming for MacRoman encoding

I was getting the following error on our hosting's server which uses Linux 3.9.3-x86_64-linode33 and 5.3.10-1ubuntu3.6. The iconv library that was used is glibc v2.15.

    log.ERROR: exception 'ErrorException' with message 'iconv(): Wrong charset, conversion from `MacRoman' to `UTF-16BE' is not allowed' in 
    /var/www/h10462/sites/www/htdocs/vendor/zendframework/zendpdf/library/ZendPdf/BinaryParser/AbstractBinaryParser.php:431

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 icon to convert MacRoman encoding to other encodings on unix OS (and perhaps other OS types).