OS X: examples on current master don't work (blank screen)

[eldyer]

On my Mac machine, examples don't run correctly (current master branch, 0.11 still works fine). Windows are always empty.

According to @kvark, this could be connected to #963.

I noticed that, in contrast to my windows machine, double_buffer is always false. See output at start:

Pixel format of the window's GL context: PixelFormat { hardware_accelerated: true, color_bits: 24, alpha_bits: 8, depth_bits: 24, stencil_bits: 8, stereoscopy: false, double_buffer: false, multisampling: None, srgb: true }
OpenGL version 4.1 NVIDIA-10.28.10 355.11.10.10.20.111