Prototype use of "gmagick" extension

[mike42]

The ImageMagick fork, GraphicsMagick also has a PHP extension.

Port image handling to use it, for inclusion in escpos-php.

http://php.net/manual/en/book.gmagick.php

$ apt-cache search graphicsmagick | grep php
php-gmagick - Provides a wrapper to the GraphicsMagick library