Enable high resolution on osx

Enable high resolution on osx

This consists of setting a flag in the Info.plist. Everything in the
game is resolution-independent, of course, and has been thoroughly
tested on other platforms. The only issue I found is cosmetic: The
rounded window corners become more dramatic and don't look as good
against the square status bar.

Increasing the resolution also exposes two graphical quirks that I
don't think are new. Curved rails in Tracks seem to be made of short
segments that don't quite connect, but I don't see this on Android,
and on closer inspection this is already present on low resolution in
OS X. Lines in Untangle, and also Galaxies, that are at a multiple of
45 degrees seem thinner than other lines, but I also see this on
Android — I think it's just more obvious on high resolution, and could
be adjusted with antialiasing. Everything else looks as it should, for
example when moving a window between low and high dpi displays.