MSTile16x16 [ShapeNumber.w,]Xpos.w,Ypos.w ; Block-blit 16x16 shape&cook 2 bitmap, size 16x16, align x/y

Performs a highly optimised stencil-blit of the currently-used or specified
chunky Shape to the currently used chunky Bitmap at Xpos,Ypos. The Shape should
be 16x16 in size and *both* Xpos and Ypos should be multiples of 16. The Shape's
graphic will be blitted to the Bitmap's graphic, and the Shape's cookie will be
blitted to the Bitmap's stencil.