OSX HiDPI: fix most places, central DR view is still broken
OSX HiDPI: revert changes to map.c from last commit

since osmgpsmap will draw pixelated map anyway
OSX HiDPI: fix logo in bg of zonesystem
OSX HiDPI: fix slideshow view
OSX HiDPI: return correct mipmap level for HiDPI screens
OSX HiDPI: fix central DR view
OSX HiDPI: update package building instructions
OSX HiDPI: add config option and disable for old cairo
Merge pull request #778 from parafin/macosx

Retina support