Filters for FlxSprites and FlxText

I have to say that BitmapFilters seem not to be working for neko and cpp, im just posted on the nme forums.

It seems strange to me since, cpp classes for most BitmapFilters do exist, and i had the idea that they worked before.

Anyway hopefully its just a matter of time before filters and shaders are added to cpp now that nme uses OpenGl es 2.

Sorry, i just sent this pull request to flixelNME branch (its the default one), is there anything i can do about that?