2D Rasterization Texture Mapping Progress (Patreon)

The pivot was implemented, and the texture mapping is nearly good enough.

Due to the support for free rotation, we can't rely on the texture scaling to handle screen aspect customization, since the texture scaling is done in texture space and the texture space may be rotated.

So, I'm going to implement an extra parameter to handle the screen aspect scaling. This will scale the texture mapping in screen space after all other transformations are done. A single parameter (aspectx) for it may be enough, but I guess a second parameter may be useful if multiple screen aspect compensation styles (e.g. fit inside, fit outside, etc) are implemented.

In the end, this 2D rasterizer would actually be quite good for creating 2D games if a 2D polygon renderer was implemented to do the clipping.