MSTile16x16Store [ShapeNumber.w,]Xpos.w,Ypos.w ; Block-blit 16x16 shape&cook 2 bitmaps, size 16x16, align x/y

Does the same as MSTile16x16 except that the Shape's graphic will *also* be placed
onto the *second* currently-used chunky Bitmap's image. This is mainly so that a
background-store Bitmap can be created for use with Bitmap-based un-queue
operations.