Added events for dynamically connecting and disconnecting displays, with an iOS implementation

include/SDL_video.h

@@ -175,7 +175,9 @@ typedef enum
 typedef enum
 {
     SDL_DISPLAYEVENT_NONE,          /**< Never used */
-    SDL_DISPLAYEVENT_ORIENTATION    /**< Display orientation has changed to data1 */
+    SDL_DISPLAYEVENT_ORIENTATION,   /**< Display orientation has changed to data1 */
+    SDL_DISPLAYEVENT_CONNECTED,     /**< Display has been added to the system */
+    SDL_DISPLAYEVENT_DISCONNECTED,  /**< Display has been removed from the system */
 } SDL_DisplayEventID;
 
 typedef enum