always define PRI?64 using 'I64' when targeting windows

avoids -Wformat warnings from mingw toolchains -- e.g.:
src/test/SDL_test_harness.c:581:37: warning: unknown conversion type character 'l' in format [-Wformat=]

(cherry picked from commit 49b6c24722e3c193f1093c728791ad5692766818)

include/SDL_stdinc.h

@@ -265,10 +265,10 @@ typedef uint64_t Uint64;
  * <stdint.h> should define these but this is not true all platforms.
  * (for example win32) */
 #ifndef SDL_PRIs64
-#ifdef PRIs64
-#define SDL_PRIs64 PRIs64
-#elif defined(__WIN32__) || defined(__GDK__)
+#if defined(__WIN32__) || defined(__GDK__)
 #define SDL_PRIs64 "I64d"
+#elif defined(PRIs64)
+#define SDL_PRIs64 PRIs64
 #elif defined(__LP64__) && !defined(__APPLE__)
 #define SDL_PRIs64 "ld"
 #else
@@ -276,10 +276,10 @@ typedef uint64_t Uint64;
 #endif
 #endif
 #ifndef SDL_PRIu64
-#ifdef PRIu64
-#define SDL_PRIu64 PRIu64
-#elif defined(__WIN32__) || defined(__GDK__)
+#if defined(__WIN32__) || defined(__GDK__)
 #define SDL_PRIu64 "I64u"
+#elif defined(PRIu64)
+#define SDL_PRIu64 PRIu64
 #elif defined(__LP64__) && !defined(__APPLE__)
 #define SDL_PRIu64 "lu"
 #else
@@ -287,10 +287,10 @@ typedef uint64_t Uint64;
 #endif
 #endif
 #ifndef SDL_PRIx64
-#ifdef PRIx64
-#define SDL_PRIx64 PRIx64
-#elif defined(__WIN32__) || defined(__GDK__)
+#if defined(__WIN32__) || defined(__GDK__)
 #define SDL_PRIx64 "I64x"
+#elif defined(PRIx64)
+#define SDL_PRIx64 PRIx64
 #elif defined(__LP64__) && !defined(__APPLE__)
 #define SDL_PRIx64 "lx"
 #else
@@ -298,10 +298,10 @@ typedef uint64_t Uint64;
 #endif
 #endif
 #ifndef SDL_PRIX64
-#ifdef PRIX64
-#define SDL_PRIX64 PRIX64
-#elif defined(__WIN32__) || defined(__GDK__)
+#if defined(__WIN32__) || defined(__GDK__)
 #define SDL_PRIX64 "I64X"
+#elif defined(PRIX64)
+#define SDL_PRIX64 PRIX64
 #elif defined(__LP64__) && !defined(__APPLE__)
 #define SDL_PRIX64 "lX"
 #else