macosx: expose the 'Karaoke' filter in the UI because we can

Manual backport of 79a5d68775e135b0f7337d5300a03875588f459d since it doesn't introduce new strings.

NEWS

@@ -43,6 +43,7 @@ Mac OS X:
  * Improve system sleep behavior when playing audio-only media. The screen is
    allowed to sleep while the system is kept awake during playback.
  * Fix code signing of Delete Preferences application
+ * Add option to Audio Effects panel to activate the Karaoke filter
 
 Miscellaneous:
  * Fix Notify (D-Bus) plugin deadlock.

modules/gui/macosx/AudioEffects.h

@@ -96,6 +96,7 @@
     IBOutlet id o_filter_normLevel_ckb;
     IBOutlet id o_filter_normLevel_sld;
     IBOutlet id o_filter_normLevel_lbl;
+    IBOutlet id o_filter_karaoke_ckb;
 }
 
 /* generic */
@@ -132,5 +133,6 @@
 - (IBAction)filter_enableHeadPhoneVirt:(id)sender;
 - (IBAction)filter_enableVolumeNorm:(id)sender;
 - (IBAction)filter_volNormSliderUpdated:(id)sender;
+- (IBAction)filter_enableKaraoke:(id)sender;
 
 @end

modules/gui/macosx/AudioEffects.m

@@ -97,6 +97,7 @@ static VLCAudioEffects *_o_sharedInstance = nil;
     [o_filter_headPhone_ckb setTitle:_NS("Headphone virtualization")];
     [o_filter_normLevel_ckb setTitle:_NS("Volume normalization")];
     [o_filter_normLevel_lbl setStringValue:_NS("Maximum level")];
+    [o_filter_karaoke_ckb setTitle:_NS("Karaoke")];
 
     /* generic */
     [[o_tableView tabViewItemAtIndex:[o_tableView indexOfTabViewItemWithIdentifier:@"equalizer"]] setLabel:_NS("Equalizer")];
@@ -609,10 +610,12 @@ static bool GetEqualizerStatus( intf_thread_t *p_custom_intf,
     {
         [o_filter_headPhone_ckb setState: (NSInteger)strstr( psz_afilters, "headphone" ) ];
         [o_filter_normLevel_ckb setState: (NSInteger)strstr( psz_afilters, "normvol" ) ];
+        [o_filter_karaoke_ckb setState: (NSInteger)strstr( psz_afilters, "karaoke" ) ];
         free( psz_afilters );
     } else {
         [o_filter_headPhone_ckb setState: NSOffState];
         [o_filter_normLevel_ckb setState: NSOffState];
+        [o_filter_karaoke_ckb setState: NSOffState];
     }
     [o_filter_normLevel_sld setFloatValue: config_GetFloat( p_intf, "norm-max-level" )];
 }
@@ -640,4 +643,9 @@ static bool GetEqualizerStatus( intf_thread_t *p_custom_intf,
     config_PutFloat( p_intf, "norm-max-level", [o_filter_normLevel_sld floatValue] );
 }
 
+- (IBAction)filter_enableKaraoke:(id)sender
+{
+    [self setAudioFilter: "karaoke" on:[sender state]];
+}
+
 @end