Remove almost all instances of "volatile" keyword.

As Tiffany pointed out in Bugzilla, volatile is not useful for thread safety:

https://software.intel.com/en-us/blogs/2007/11/30/volatile-almost-useless-for-multi-threaded-programming/

Some of these volatiles didn't need to be, some were otherwise protected by
spinlocks or mutexes, and some got moved over to SDL_atomic_t data, etc.

Fixes Bugzilla #3220.

src/haptic/windows/SDL_windowshaptic_c.h

@@ -42,8 +42,8 @@ struct haptic_hwdata
     Uint8 userid; /* XInput userid index for this joystick */
     SDL_Thread *thread;
     SDL_mutex *mutex;
-    volatile Uint32 stopTicks;
-    volatile int stopThread;
+    Uint32 stopTicks;
+    SDL_atomic_t stopThread;
 };