SDL_test: introduce SDLTest_CommonDestroyState to only destroy SDLTest_CommonState

include/SDL3/SDL_test_common.h

@@ -122,7 +122,7 @@ typedef struct
     int gl_debug;
     int gl_profile_mask;
 
-    /* Additional fields added in 2.0.18 */
+    /* Mouse info */
     SDL_Rect confine;
 
 } SDLTest_CommonState;
@@ -145,6 +145,13 @@ extern "C" {
  */
 SDLTest_CommonState *SDLTest_CommonCreateState(char **argv, Uint32 flags);
 
+/**
+ * \brief Free the common state object.
+ *
+ * \param state The common state object to destroy
+ */
+void SDLTest_CommonDestroyState(SDLTest_CommonState *state);
+
 /**
  * \brief Process one common argument.
  *