Bring Xcode up to 4.6 standards.

Basically includes hi def image stuff and headers.

Note: Mac OS X build is broken. LowLevelWindow_MacOSX.mm refers to the removed RageDisplay_Legacy_Helpers files. The replacement is not immediately obvious.

src/arch/Sound/RageSoundDriver_AU.cpp

@@ -4,6 +4,8 @@
 #include "PrefsManager.h"
 #include "archutils/Darwin/DarwinThreadHelpers.h"
 #include <CoreServices/CoreServices.h>
+#include <AudioToolbox/AudioServices.h>
+#include <CoreAudio/CoreAudio.h>
 
 REGISTER_SOUND_DRIVER_CLASS2( AudioUnit, AU );