NAME
        MoveLayer -- move layer to new position in bitmap.

    SYNOPSIS
        result = MoveLayer( dummy, l, dx, dy )
        d0                  a0     a1 d0  d1

        long movelayer( long, struct layer *, long, long);

    FUNCTION
        move this layer to new position in shared bitmap.
        If any refresh layers become revealed, collect damage and
        set REFRESH bit in layer Flags.

    INPUTS
        dummy - unused
        l - pointer to a nonbackdrop layer
        dx - delta to add to current x position
        dy - delta to add to current y position

    RETURNS
        result - TRUE if operation successful
                 FALSE if failed (out of memory)

    BUGS
        May not handle (dx,dy) which attempts to move the layer outside the
        layer's RastPort->BitMap bounds .

    SEE ALSO
        graphics/layers.h, graphics/clip.h