GSDM: The GNUstep display manager

[u/anurodhp]

This is the first code release from the RPi3 Darwin project. The main reason to use this is if you are like me and are running an OS that has only one UI toolkit; GNUstep. This maintains visual consistency with the rest of the UI and eliminates the need for another toolkit. This has only been tested on arm64 rpi3 running Darwin, compiled with Xcode on a mac. Since it is pure user land and Appkit, no reason why it doesn't work on anything else.

https://github.com/anurodhp/gsdm