Function vkGetPhysicalDeviceXlibPresentationSupportKHR 

pub unsafe extern "system" fn vkGetPhysicalDeviceXlibPresentationSupportKHR(
    physicalDevice: VkPhysicalDevice,
    queueFamilyIndex: u32,
    dpy: *mut Display,
    visualID: VisualID,
) -> VkBool32

Available if built with prototypes.