MMaskScrollStencil X1.w,Y1.w,Width.w,Height.w,X2.w,Y2.w[,SourceBitmapNum.w];Copy stencil2stencil & stencil-cut

Does the same as MMaskScroll but with regards to the stencil of chunky Bitmap
objects. Source and destination are chunky Bitmap object's stencils. The source
Bitmap's stencil will be mask-blitted onto the destination Bitmap's stencil.