SweepEvent comparison error thrown for infinitely thin input polygons

[mfogel]

If a polygon has an internal segment that is infinitely thin, polygon-clipping can crash. For example, performing a union on the following shapes results in a SweepEvent comparison failed at [-1, 0]... equal but not identical?

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [[-2, -1], [-1, 0], [1, 0], [2, -1], [2, 1], [1, 0], [-1, 0], [-2, 1]]
        ]
      }
    },
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Polygon",
        "coordinates": [[[-3, -3], [3, -3], [3, 3], [-3, 3], [-3, -3]]]
      }
    }
  ]
}

The polygon above polygon causing the problem looks like this:

What's going on here is that the algorithm doesn't know how to sort the two segments from the same ring that both go from [-1, 0] to [1, 0].

[mfogel]

Other sets of coordinates that have appeared in the wild that appear to trigger this bug (pulled over from #41):

var coords = [
  [
    [-118.46571, 34.025348],
    [-118.465871, 34.025308],
    [-118.465936, 34.025348],
    [-118.467899, 34.025348],
    [-118.468194, 34.025197],
    [-118.468983, 34.025174],
    [-118.469245, 34.025348],
    [-118.46571, 34.025348]
  ]
];

polygonClipping.union(
  JSON.parse(JSON.stringify(coords)),
  JSON.parse(JSON.stringify(coords))
); // or `polygonClipping.union(coords, coords)`

polygonClipping.union(
  [
    [
      [-118.46571, 34.025348],
      [-118.465871, 34.025308],
      [-118.465936, 34.025348],
      [-118.467899, 34.025348],
      [-118.468194, 34.025197],
      [-118.468983, 34.025174],
      [-118.469245, 34.025348],
      [-118.46571, 34.025348]
    ]
  ],
  [
    [
      [-118.464605, 34.02561],
      [-118.465871, 34.025308],
      [-118.466413, 34.02565],
      [-118.467722, 34.025468],
      [-118.468194, 34.025197],
      [-118.468983, 34.025174],
      [-118.469433, 34.025494],
      [-118.470297, 34.025512],
      [-118.472282, 34.027219],
      [-118.464605, 34.02561]
    ]
  ]
);

[brianhearn]

Any luck with this one? I'm trying to use this with union operation on postal code polygons and running into it frequently