macOS: Double check if the CGEventFlags correctly get set

[pentamassiv]

In order to get rid of the sleep statements on macOS, the modifier flags need to be set manually. I looked at the flags from the previous implementation and set them the same way manually. There were known issues with the previous implementation so it probably is not 100% correct. The old implementation did not correctly set the CapsLock/ShiftLock flags. It also didn't set them correctly when using the fast_text function. We should observe real keypresses and copy their behavior instead. I am especially concerned with the "sticky keys" mentioned in PR #329. Those might be wrong.