VulkanRenderer: implement metal view

The metal view backing the MoltenVK compatibility wrapper is written in
Obj-C.

It would have been possible to use the Objective-C runtime in C++ but
the code is less performant (the symbol binding is done at first use
instead of the beginning of the program) and actually harder to get
right.

Note that MoltenVK is not linked to the loader, so the libMoltenVK.dylib
object must be available for loading.

include/Nazara/VulkanRenderer/Wrapper/Surface.hpp

@@ -12,6 +12,11 @@
 #include <Nazara/VulkanRenderer/Wrapper/Instance.hpp>
 #include <Nazara/VulkanRenderer/Wrapper/Loader.hpp>
 
+#ifdef VK_USE_PLATFORM_METAL_EXT
+#include <objc/runtime.h>
+#include <vulkan/vulkan_metal.h>
+#endif
+
 namespace Nz 
 {
 	namespace Vk
@@ -54,6 +59,11 @@ namespace Nz
 				inline bool Create(HINSTANCE instance, HWND handle, VkWin32SurfaceCreateFlagsKHR flags = 0, const VkAllocationCallbacks* allocator = nullptr);
 				#endif
 
+				#ifdef VK_USE_PLATFORM_METAL_EXT
+				inline bool Create(const VkMetalSurfaceCreateInfoEXT& createInfo, const VkAllocationCallbacks* allocator = nullptr);
+				inline bool Create(id layer, const VkAllocationCallbacks* allocator = nullptr);
+				#endif
+
 				inline void Destroy();
 
 				bool GetCapabilities(VkPhysicalDevice physicalDevice, VkSurfaceCapabilitiesKHR* surfaceCapabilities) const;