Improved the performance of love.window.getPixelScale / toPixels / fromPixels by caching some values. Made some coordinate space-sensitive code use the proper conversions to get to the correct coordinate space.

--HG--
branch : minor

src/modules/sound/lullaby/CoreAudioDecoder.cpp

@@ -50,7 +50,7 @@ OSStatus readFunc(void *inClientData, SInt64 inPosition, UInt32 requestCount, vo
 	else
 	{
 		*actualCount = 0;
-		return kAudioFileUnspecifiedError;
+		return kAudioFilePositionError;
 	}
 
 	return noErr;