Update SDL_begin_code.h

Co-authored-by: Sam Lantinga <slouken@libsdl.org>

Author: icculus

include/SDL3/SDL_begin_code.h

@@ -537,7 +537,7 @@
 #elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
 #define SDL_ALIGNED(x) _Alignas(x)
 #else
-#define SDL_ALIGNED(x) SDL_ALIGNED_is_not_supported_by_this_compiler___THIS_IS_A_SERIOUS_PROBLEM
+#define SDL_ALIGNED(x) PLEASE_DEFINE_SDL_ALIGNED
 #endif
 #endif /* SDL_ALIGNED not defined */