Add sdl-ttf

Add sdl-ttf

can be used as follows:


    font := TTF open("./assets/FreeMono.ttf", 32)
    text := font renderUTF8Solid("测试,テスト,test" toCString(), (0,0,0,0) as SdlColor)
    texture := SDL createTextureFromSurface(renderer, text)
	SDL setRenderDrawColor(renderer, 0, 40, 80, 255)
	SDL renderClear(renderer)
	SDL renderCopy(renderer, texture, null, null)


the word "Ttf" looks ugly, maybe I should replace it with "ttf"?