Tweak Vulkan include guard check and 64-bit platform defines (#13210)

Author: e4m2

include/SDL3/SDL_vulkan.h

@@ -51,14 +51,14 @@
 extern "C" {
 #endif
 
-/* Avoid including vulkan.h, don't define VkInstance if it's already included */
-#ifdef VULKAN_H_
+/* Avoid including vulkan_core.h, don't define VkInstance if it's already included */
+#ifdef VULKAN_CORE_H_
 #define NO_SDL_VULKAN_TYPEDEFS
 #endif
 #ifndef NO_SDL_VULKAN_TYPEDEFS
 #define VK_DEFINE_HANDLE(object) typedef struct object##_T* object;
 
-#if defined(__LP64__) || defined(_WIN64) || defined(__x86_64__) || defined(_M_X64) || defined(__ia64) || defined (_M_IA64) || defined(__aarch64__) || defined(__powerpc64__)
+#if defined(__LP64__) || defined(_WIN64) || (defined(__x86_64__) && !defined(__ILP32__)) || defined(_M_X64) || defined(__ia64) || defined (_M_IA64) || defined(__aarch64__) || defined(__powerpc64__) || (defined(__riscv) && __riscv_xlen == 64)
 #define VK_DEFINE_NON_DISPATCHABLE_HANDLE(object) typedef struct object##_T *object;
 #else
 #define VK_DEFINE_NON_DISPATCHABLE_HANDLE(object) typedef uint64_t object;