Move Mac OS build to use osxfuse

Hi Jakob,

could you review and merge the following pull request, please? The Mac OS X build is now using osxfuse, since fuse4x isn't further developed anymore. To support the new setup on the build machines I would suggest to  install https://github.com/downloads/osxfuse/osxfuse/OSXFUSE-2.5.4.dmg and to completely remove fuse4x. The former fuse4x dmg contains an uninstall script and the packages are still available at http://fuse4x.github.com. 

Thanks,
Manuel