Support ROLLSPRITE and FLATSPRITE in software renderer

[argv]

Please consider implementing the ROLLSPRITE and FLATSPRITE flags in the software renderer. These flags make it possible to make much nicer looking rotating animations, but their usability is limited by the fact that, if the player is using the software renderer, they don't apply at all!

I imagine there's a reason why the software renderer doesn't implement these (performance?), but I couldn't find anyone actually requesting this, so here it is.

[Major Cooke]

If I recall correctly, Graf and/or dpJudas are potentially still working on bits and pieces of the code and getting more stuff split up first, then stuff like this can come later.