Possibly fixed bug #601, definitely fixed a potential issue with threads

stopping and starting in rapid succession.

src/thread/SDL_thread.c

@@ -140,9 +140,11 @@ SDL_DelThread(SDL_Thread * thread)
     }
     SDL_mutexV(thread_lock);
 
+#if 0   /* There could be memory corruption if another thread is starting */
     if (SDL_Threads == NULL) {
         SDL_ThreadsQuit();
     }
+#endif
 }
 
 /* The default (non-thread-safe) global error variable */