winecoreaudio: Add stub implementation of CoreAudio_wiAudioUnitIOProc.

It will serve as the input callback called when our Audio Unit has sound
data available.
diff --git a/dlls/winmm/winecoreaudio/audio.c b/dlls/winmm/winecoreaudio/audio.c
index 1f3e6a7..0ab9109 100644
--- a/dlls/winmm/winecoreaudio/audio.c
+++ b/dlls/winmm/winecoreaudio/audio.c
@@ -208,6 +208,12 @@
                                      UInt32 inBusNumber, 
                                      UInt32 inNumberFrames, 
                                      AudioBufferList *ioData);
+OSStatus CoreAudio_wiAudioUnitIOProc(void *inRefCon,
+                                     AudioUnitRenderActionFlags *ioActionFlags,
+                                     const AudioTimeStamp *inTimeStamp,
+                                     UInt32 inBusNumber,
+                                     UInt32 inNumberFrames,
+                                     AudioBufferList *ioData);
 
 /* These strings used only for tracing */
 
@@ -1685,6 +1691,17 @@
     return MMSYSERR_NOTSUPPORTED;
 }
 
+
+OSStatus CoreAudio_wiAudioUnitIOProc(void *inRefCon,
+                                     AudioUnitRenderActionFlags *ioActionFlags,
+                                     const AudioTimeStamp *inTimeStamp,
+                                     UInt32 inBusNumber,
+                                     UInt32 inNumberFrames,
+                                     AudioBufferList *ioData)
+{
+    return noErr;
+}
+
 #else
 
 /**************************************************************************