Cocoa: Fix deprecation warning for kUTTypeURL

We switched to kUTTypeURL when NSURLPboardType was deprecated, as the
official replacement symbol NSPasteboardTypeURL was not available on
every version of macOS supported by GLFW.

kUTTypeURL has now also been deprecated.

This commit moves to a compile-time choice between NSURLPboardType and
NSPasteboardTypeURL depending on the minimum targeted macOS version.

Fixes #2003

(cherry picked from commit 7f6aa587f8)

src/cocoa_platform.h

@@ -62,6 +62,10 @@ typedef void* id;
  #define NSWindowStyleMaskTitled NSTitledWindowMask
 #endif
 
+#if MAC_OS_X_VERSION_MIN_REQUIRED < 101300
+ #define NSPasteboardTypeURL NSURLPboardType
+#endif
+
 typedef VkFlags VkMacOSSurfaceCreateFlagsMVK;
 typedef VkFlags VkMetalSurfaceCreateFlagsEXT;