High-resolution window chrome on Mac apps

This sets the correct Info.plist setting to allow for high-resolution window chrome.

See [High Resolution Guidelines for OS X](https://developer.apple.com/library/mac/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Explained/Explained.html#//apple_ref/doc/uid/TP40012302-CH4-SW11) for more info.