[MediaPlayer] Update bindings to Xcode 9.3 Beta 1 (#3330)

Diff files:
* https://github.com/xamarin/xamarin-macios/wiki/MediaPlayer-iOS-xcode9.3-beta1
* https://github.com/xamarin/xamarin-macios/wiki/MediaPlayer-tvOS-xcode9.3-beta1

src/MediaPlayer/MPVolumeSettings.cs

@@ -17,13 +17,16 @@ namespace XamCore.MediaPlayer {
 
 	// MPVolumeSettings.h
 	public static class MPVolumeSettings {
+		[Deprecated (PlatformName.iOS, 11,3, message: "Use 'MPVolumeView' to present volume controls.")]
 		[DllImport (Constants.MediaPlayerLibrary, EntryPoint="MPVolumeSettingsAlertShow")]
 		public extern static void AlertShow ();
 
+		[Deprecated (PlatformName.iOS, 11,3, message: "Use 'MPVolumeView' to present volume controls.")]
 		[DllImport (Constants.MediaPlayerLibrary, EntryPoint="MPVolumeSettingsAlertHide")]
 		public extern static void AlertHide ();
 
 		// note: sizeof (BOOL) is 1 like C, i.e. it's not a Win32 BOOL (4 bytes)
+		[Deprecated (PlatformName.iOS, 11,3, message: "Use 'MPVolumeView' to present volume controls.")]
 		[DllImport (Constants.MediaPlayerLibrary, EntryPoint="MPVolumeSettingsAlertIsVisible")]
 		[return: MarshalAs (UnmanagedType.I1)]
 		public extern static /* BOOL */ bool AlertIsVisible ();

src/mediaplayer.cs

@@ -1172,7 +1172,13 @@ namespace XamCore.MediaPlayer {
 	[NoMac]
 	[NoTV]
 	[BaseType (typeof (NSObject))]
+	[DisableDefaultCtor]
 	interface MPMusicPlayerController : MPMediaPlayback {
+
+		[Export ("init")]
+		[Deprecated (PlatformName.iOS, 11,3)]
+		IntPtr Constructor ();
+
 		[Static, Export ("applicationMusicPlayer")]
 		MPMusicPlayerController ApplicationMusicPlayer { get; }
 
@@ -2043,8 +2049,14 @@ namespace XamCore.MediaPlayer {
 	[NoMac]
 	[NoTV]
 	[iOS (10,1)]
+	[DisableDefaultCtor]
 	[BaseType (typeof (NSObject))]
-	interface MPMusicPlayerQueueDescriptor : NSSecureCoding {}
+	interface MPMusicPlayerQueueDescriptor : NSSecureCoding {
+
+		[Export ("init")]
+		[Deprecated (PlatformName.iOS, 11,3)]
+		IntPtr Constructor ();
+	}
 
 	[NoMac]
 	[NoTV]