NAME
        BehindLayer -- Put layer behind other layers.

    SYNOPSIS
        result = BehindLayer( dummy, l )
        d0                    a0     a1

        long behindlayer( long, struct layer *);

    FUNCTION
        move this layer to the most behind position swapping bits
        in and out of the display with other layers.
        If other layers are REFRESH then collect their damage lists and
        set the LAYERREFRESH bit in the Flags fields of those layers that
        may be revealed.  If this layer is a backdrop layer then
        put this layer behind all other backdrop layers.
        If this layer is NOT a backdrop layer then put in front of the
        top backdrop layer and behind all other layers.

        Note: this operation may generate refresh events in other layers
           associated with this layer's layer_info structure.

    INPUTS
        dummy - unused
        l - pointer to a layer

    RESULTS
        result - TRUE    if operation successful
                 FALSE   if operation unsuccessful (probably out of memory)

    BUGS

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