FloodFill() small changes
FloodFill() small changes

Removed unnecessary image.Mutate, added doc coment, deleted old System.Drawin impl., fixes for border version

peachpiecompiler/peachpie,iolevel/peachpie,iolevel/peachpie-concept,iolevel/peachpie-concept,peachpiecompiler/peachpie,iolevel/peachpie,iolevel/peachpie,peachpiecompiler/peachpie,iolevel/peachpie-concept