ios: add shutdown to dealloc player resource

ios/IJKMediaPlayer/IJKMediaPlayer/IJKFFMoviePlayerController.m

@@ -135,6 +135,14 @@
     return ijkmp_is_playing(_mediaPlayer);
 }
 
+- (void)shutdown
+{
+    if (!_mediaPlayer)
+        return;
+
+    ijkmp_shutdown(_mediaPlayer);
+}
+
 - (MPMoviePlaybackState)playbackState
 {
     if (!_mediaPlayer)

ios/IJKMediaPlayer/IJKMediaPlayer/IJKMPMoviePlayerController.m

@@ -72,6 +72,11 @@
     }
 }
 
+- (void)shutdown
+{
+    // do nothing
+}
+
 #pragma mark Movie Notification Handlers
 
 /* Register observers for the various movie object notifications. */

ios/IJKMediaPlayer/IJKMediaPlayer/IJKMediaPlayback.h

@@ -37,6 +37,7 @@
 - (void)pause;
 - (void)stop;
 - (BOOL)isPlaying;
+- (void)shutdown;
 
 @property(nonatomic, readonly)  UIView *view;
 @property(nonatomic)            NSTimeInterval currentPlaybackTime;