reset playback position on stop (same behavior like in BASS)

Vocaluxe/Lib/Sound/COpenALPlay.cs

@@ -568,6 +568,7 @@ namespace Vocaluxe.Lib.Sound
         public void Stop()
         {
             AL.SourceStop(_source);
+            Skip(0f);
         }
 
         public bool Loop

Vocaluxe/Lib/Sound/CPortAudioPlay.cs

@@ -549,6 +549,7 @@ namespace Vocaluxe.Lib.Sound
         public void Stop()
         {
             errorCheck("StartStream", PortAudio.Pa_StopStream(_Ptr));
+            Skip(0f);
         }
 
         public bool Loop