Define SDL_PLATFORM_* macros instead of underscored ones (#8875)

test/testgles.c

@@ -14,7 +14,7 @@
 #include <SDL3/SDL_test_common.h>
 #include <SDL3/SDL_main.h>
 
-#if defined(__IOS__) || defined(__ANDROID__)
+#if defined(SDL_PLATFORM_IOS) || defined(SDL_PLATFORM_ANDROID)
 #define HAVE_OPENGLES
 #endif
 
@@ -335,7 +335,7 @@ int main(int argc, char *argv[])
         SDL_Log("%2.2f frames per second\n",
                 ((double)frames * 1000) / (now - then));
     }
-#ifndef __ANDROID__
+#ifndef SDL_PLATFORM_ANDROID
     quit(0);
 #endif
     return 0;