Metal backend - memory leak

[thevojacek]

When using managing GLFW on your own, using example3 for instance, there is quite serious memory leakage when running on MacOS using Metal renderer. It is presumably due to non-releasing Metal drawables when proceeding using example3. There is obviously workaround to use something like screen->drawAll() which releases those resources and then somehow manually manage usage of system resources by thread sleeping for instance. However, this is not very convenient doing on this level, because it requires checking for incoming window events as well to determine when to start redrawing UI...

Basically what i wanted to point-out is that example3 is unusable with Metal backend as it consumes enormous amount of memory over time and also keep requesting new ports from OS.