MBitmapYFlip BitmapNumber.w ; Vertically flip a Bitmap (see MAutoStencilFlip)

Flips a previously-created chunky Bitmap's graphic vertically. The operation may
also be performed on the stencil if MAutoStencilYFlip or MAutoStencilFlip have
ben activated. The area of the Bitmap to be flipped can be cropped using the
Bitmap's clip window.