NAME
    XorRegionRegion -- Perform 2d XOR operation of one region
                       with second region, leaving result in second region

SYNOPSIS
    status = XorRegionRegion(region1,region2)
    d0                        a0      a1

    BOOL XorRegionRegion( struct region *, struct region * );

FUNCTION
    Join the regions together. If any part of region1 overlaps
    region2 then remove that from the new region.

INPUTS
    region1      = pointer to region structure
    region2      = pointer to region structure

RESULTS
    status - return TRUE if successful operation
             return FALSE if ran out of memory

BUGS