Remove SDL_config.h from the public headers

The SDL headers are no longer dependent on the build configuration.

Fixes https://github.com/libsdl-org/SDL/issues/6643 and https://github.com/libsdl-org/SDL/issues/6641

test/testime.c

@@ -13,10 +13,6 @@
    If you build without SDL_ttf, you can use the GNU Unifont hex file instead.
    Download at http://unifoundry.com/unifont.html */
 
-#include <stdlib.h>
-#include <stdio.h>
-#include <string.h>
-
 #include "SDL.h"
 #ifdef HAVE_SDL_TTF
 #include "SDL_ttf.h"
@@ -806,5 +802,4 @@ int main(int argc, char *argv[])
     return 0;
 }
 
-
 /* vi: set ts=4 sw=4 expandtab: */