set flag RegionBorder_innerPoints_debug.

svoid test_RegionBorder_innerPoints_withDiagonals_thinSpike() {
  BWImage img = bwImageFromString([[
    ______
    _xxxx_
    _xx___
    ______
  ]]);
  FastRegions_BWImage regions = new(img);
  regions.run();
  assertEqualsVerbose(2, regions.nRegions());
  RegionBorder_innerPoints_withDiagonals border = new(regions.getRegion(2));
  var points = border.allPoints();
  //removeLastIfSameAsFirst(points);
  assertEqualsVerbose("4448782", str(border.onePath()));
}

Began life as a copy of #1034904