Use new api.

stepmania/src/arch/InputHandler/InputHandler_Carbon.cpp

@@ -705,7 +705,7 @@ int InputHandler_Carbon::Run( void *data )
 	CFRetain( This->mLoopRef );
 	
 	This->StartDevices();
-	SetThreadPrecedence( 100 );
+	SetThreadPrecedence( 1.0f );
 
 	/* The function copies the information out of the structure, so the memory pointed
 	 * to by context does not need to persist beyond the function call. */

stepmania/src/arch/Sound/RageSoundDriver_CA.cpp

@@ -341,7 +341,7 @@ OSStatus RageSound_CA::JackChanged( AudioDeviceID inDevice, UInt32 inChannel, Bo
 void RageSound_CA::SetupDecodingThread()
 {
 	/* Increase the scheduling precedence of the decoder thread. */
-	SetThreadPrecedence( 50 );
+	SetThreadPrecedence( 0.75f );
 }
 
 /*