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/testdrawchessboard.c

@@ -14,9 +14,6 @@
 
 /* Sample program:  Draw a Chess Board  by using SDL_CreateSoftwareRenderer API */
 
-#include <stdlib.h>
-#include <stdio.h>
-
 #ifdef __EMSCRIPTEN__
 #include <emscripten/emscripten.h>
 #endif
@@ -145,3 +142,4 @@ main(int argc, char *argv[])
     return 0;
 }
 
+/* vi: set ts=4 sw=4 expandtab: */