NAME
	InstallClipRegion -- Install clip region in layer

    SYNOPSIS
	oldclipregion = InstallClipRegion( l,  region )
	d0                                 a0  a1

	struct Region *InstallClipRegion( struct Layer *, struct Region *);

    FUNCTION
	Installs a transparent Clip region in the layer. All
	subsequent graphics calls will be clipped to this region.
	You MUST remember to call InstallClipRegion(l,NULL) before
	calling DeleteLayer(l) or the Intuition function CloseWindow()
 	if you have installed a non-NULL ClipRegion in l.

    INPUTS
	l - pointer to a layer
	region - pointer to a region

    RESULTS
	oldclipregion - The pointer to the previous ClipRegion that
	    was installed. Returns NULL if no previous ClipRegion installed.

	    Note: If the system runs out of memory while computing the
	        resulting ClipRects the LAYERS_CLIPRECTS_LOST bit will
	        be set in l->Flags.

    BUGS
	If the system runs out of memory during normal layer operations,
	the ClipRect list may get swept away and not restored.
	As soon as there is enough memory and the layer library
	gets called again the ClipRect list will be rebuilt.

    SEE ALSO
	BeginUpdate() EndUpdate(),
	graphics/layers.h, graphics/clip.h, graphics/regions.h