NAME
    BeginUpdate -- Prepare to repair damaged layer.

SYNOPSIS
    result = BeginUpdate( l )
    d0                    a0

    LONG BeginUpdate( struct Layer *);

FUNCTION
    Convert damage list to ClipRect list and swap in for
    programmer to redraw through. This routine simulates
    the ROM library environment. The idea is to only render in the
    "damaged" areas, saving time over redrawing all of the layer.
    The layer is locked against changes made by the layer library.

INPUTS
    l - pointer to a layer

RESULTS
    result - TRUE if damage list converted to ClipRect list sucessfully.
             FALSE if list conversion aborted. (probably out of memory)

BUGS
    If BeginUpdate returns FALSE, programmer must abort the attempt to
    refresh this layer and instead call EndUpdate( l, FALSE ) to restore
    original ClipRect and damage list.

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