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 ouside the
    layer's RastPort->BitMap bounds .
SEE ALSO
    graphics/layers.h, graphics/clip.h