Make compile-time assert error messages more clear.

Now the compiler might say this:

'SDL_compile_time_assert_mytest' declared as an array with a negative size

instead of

'SDL_dummy_mytest' declared as an array with a negative size

include/SDL_stdinc.h

@@ -269,7 +269,7 @@ typedef uint64_t Uint64;
 #endif /* SDL_DISABLE_ANALYZE_MACROS */
 
 #define SDL_COMPILE_TIME_ASSERT(name, x)               \
-       typedef int SDL_dummy_ ## name[(x) * 2 - 1]
+       typedef int SDL_compile_time_assert_ ## name[(x) * 2 - 1]
 /** \cond */
 #ifndef DOXYGEN_SHOULD_IGNORE_THIS
 SDL_COMPILE_TIME_ASSERT(uint8, sizeof(Uint8) == 1);