* initial work on the restructering of the rasterization stage (similar setup to the binner, with work-groups dynamically requesting bins to be processed by them)
 * scrapped the idea of doing a coarse rasterization stage (for now; 64*64px = 4096px per bin for a work-group size of 1024 seem okay/nice)
 * store bin count and batch size+count in the draw_state, so it can be accessed across stages
 * clear atomic counters on the kernel side, not the host side (-> faster, since memory doesn't have to mapped on the host side)
 * killed rasterization constant buffer, since it's not needed any more (everything is either done implicitly (triangle count) or passed in via normal kernel parameters)
 * don't store "internal" opencl devices in an extra container any more, but in the device_object directly (this fixes some issues where internal devices != actual/used devices)
 * on os x: handle opencl device restrictions much earlier, before context creation, so the context doesn't contain unwanted devices, even if those wouldn't get accessed + handle special case where opengl sharing is enabled, but gpu devices are disallowed
 * renamed pipeline kernels to oclraster_* ("bin" or "program" for user programs)