vulkan: Update the XML and headers to 1.1.123

Acked-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

include/vulkan/vulkan_ios.h

@@ -1,10 +1,6 @@
 #ifndef VULKAN_IOS_H_
 #define VULKAN_IOS_H_ 1
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /*
 ** Copyright (c) 2015-2019 The Khronos Group Inc.
 **
@@ -27,6 +23,11 @@ extern "C" {
 */
 
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
 
 #define VK_MVK_ios_surface 1
 #define VK_MVK_IOS_SURFACE_SPEC_VERSION   2