WIP: Patch skew support

• needa figure out how the heck to fill in the gaps
• also opengl support that seems important

Lua: v.drawAffine(x, y, xscale, yscale, xskew, yskew, patch, flags, colormap)
C: V_DrawAffinePatch(fixed_t x, fixed_t y, fixed_t pscale, fixed_t vscale, fixed_t skewx, fixed_t skewy, INT32 scrn, patch_t *patch, const UINT8 *colormap);