Further *BSD portability.

git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@5958 8ced0084-cf51-0410-be5f-012b33b47a6e

Source/Core/AudioCommon/Src/Mixer.h

@@ -44,6 +44,8 @@ public:
 		INFO_LOG(AUDIO_INTERFACE, "Mixer is initialized (AISampleRate:%i, DACSampleRate:%i)", AISampleRate, DACSampleRate);
 	}
 
+	virtual ~CMixer() {}
+
 	// Called from audio threads
 	virtual unsigned int Mix(short* samples, unsigned int numSamples);
 	virtual void Premix(short *samples, unsigned int numSamples) {}