refs #372 Move voice channel sharing into CContextAudio

Before a very complex mechanism was implemented in order to share
a vatlib voice channel resource if more than one COM unit was connected
to the same channel. This is now moved into CContextAudio by mapping
a COM unit to a shared voice channel pointer.

src/blackcore/voice_vatlib.h

@@ -11,6 +11,7 @@
 
 #include <QString>
 #include <QScopedPointer>
+#include <QSharedPointer>
 
 #ifdef Q_OS_WIN
 #ifndef NOMINMAX
@@ -37,7 +38,7 @@ namespace BlackCore
         virtual ~CVoiceVatlib();
 
         //! \copydoc IVoice::createVoiceChannel()
-        virtual std::unique_ptr<IVoiceChannel> createVoiceChannel() override;
+        virtual QSharedPointer<IVoiceChannel> createVoiceChannel() override;
 
         //! \copydoc IVoice::createInputDevice()
         virtual std::unique_ptr<IAudioInputDevice> createInputDevice() override;