Build mpl on OSX has proven to be a nightmare because of all the
different types of zlib, png and freetype that may be on your system.
The recommended and supported way to build is to use the make.osx file
in this directory.  This script requires you to set a PREFIX
environment variable where you want to the install to go.  It will
fetch the dependencies from a remove server and install them into your
PREFIX dir, and then build mpl against them.  It should ignore any
lib, png or freetype on your system

Example usage::

  PREFIX=/Users/jdhunter/dev make -f make.osx fetch deps mpl_install