made two callback procedures static.

src/sound_beos.cpp

@@ -121,7 +121,7 @@ static int read_buffer(unsigned char *data, int len)
 	return len;
 }
 
-void render_proc(void *theCookie, void *buffer, size_t req, 
+static void render_proc(void *theCookie, void *buffer, size_t req, 
 				const media_raw_audio_format &format)
 {
 	size_t amt;

src/sound_coreaudio.c

@@ -103,7 +103,7 @@ static int read_buffer(unsigned char *data, int len)
 	return len;
 }
 
-OSStatus render_proc(void *inRefCon,
+static OSStatus render_proc(void *inRefCon,
 		AudioUnitRenderActionFlags *inActionFlags,
 		const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber,
 		UInt32 inNumFrames, AudioBufferList *ioData)