message: Simplify example surface format selection
  According to specs for vkGetPhysicalDeviceSurfaceFormatsKHR(), at least
  one surface format must be returned, and returned formats must not be
  VK_FORMAT_UNDEFINED.
diff: @@ -326,20 +326,10 @@ impl ExampleBase {
  let present_queue = device.get_device_queue(queue_family_index as u32, 0);
  - let surface_formats = surface_loader
  + let surface_format = surface_loader
  .get_physical_device_surface_formats(pdevice, surface)
  - .unwrap();
  - let surface_format = surface_formats
  - .iter()
  - .map(|sfmt| match sfmt.format {
  - vk::Format::UNDEFINED => vk::SurfaceFormatKHR {
  - format: vk::Format::B8G8R8_UNORM,
  - color_space: sfmt.color_space,
  - },
  - _ => *sfmt,
  - })
  - .next()
  - .expect("Unable to find suitable surface format.");
  + .unwrap()[0];
  +
  let surface_capabilities = surface_loader
  .get_physical_device_surface_capabilities(pdevice, surface)
  .unwrap();
  