All of the glfw demo headers unset shift keypresses when the ctrl key is not
also down.
I can't think of a reason this would be desired and it appears no other demo
code does this.
Unless I'm mistaken, simply removing these lines leaves us with the desired
behaviour.
The Vulkan spec states that create_info.minImageCount determines
the minimum number of images to create, not the exact count.
The count retrieved via vkGetSwapchainImagesKHR can (and in my
case does) differ - without penalty to the rest of the demo.
