Support changing 'audio desync' via AppleScript on OSX

Like being able to change the volume, seek position etc. via
AppleScript, this commit allows you to change the audio desync in ms.

Example:
tell application "VLC"
  -- set audio desync to 0
  set audio desync to -2250
  get audio desync
end tell
Signed-off-by: Boy van Amstel <boy@boyvanamstel.nl>
Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>

modules/gui/macosx/applescript.h

@@ -42,6 +42,7 @@
 
 @property (readwrite) BOOL scriptFullscreenMode;
 @property (readwrite) int audioVolume;
+@property (readwrite) int audioDesync;
 @property (readwrite) int currentTime;
 @property (readonly) int durationOfCurrentItem;
 @property (readonly) NSString *pathOfCurrentItem;

modules/gui/macosx/applescript.m

@@ -212,6 +212,28 @@
     [[VLCCoreInteraction sharedInstance] setVolume:(int)i_audioVolume];
 }
 
+- (int) audioDesync {
+    input_thread_t * p_input = pl_CurrentInput(VLCIntf);
+    int i_delay = -1;
+
+    if(!p_input)
+        return i_delay;
+
+    i_delay = var_GetTime(p_input, "audio-delay");
+    vlc_object_release(p_input);
+
+    return (i_delay / 1000);
+}
+
+- (void) setAudioDesync:(int)i_audioDesync {
+    input_thread_t * p_input = pl_CurrentInput(VLCIntf);
+    if(!p_input)
+        return;
+
+    var_SetTime(p_input, "audio-delay", i_audioDesync * 1000);
+    vlc_object_release(p_input);
+}
+
 - (int) currentTime {
     input_thread_t * p_input = pl_CurrentInput(VLCIntf);
     int64_t i_currentTime = -1;