fix: while three point in a line and the second point is in the dividing line of the tile will have problem

[DeZhao-Zhang]

Bug Fix: while three point in a line and the second point is in the dividing line of the tile(with buffer), then the point will be lost in particular level.

[DeZhao-Zhang]

Other data is ok, while the second point is in the dividing line of the tile(with buffer), this bug will happan

1. while I use data as blow

{
	"type": "FeatureCollection",
	"features": [
		{
			"type": "Feature",
			"geometry": {
				"type": "Polygon",
				"coordinates": [
					[
						[20.0, 34.365234375],
						[80.0, 4.34326171875],
						[45.0, 4.34326171875],
						[20.0, 4.34326171875],
						[20.0, 34.365234375]
					]
				]
			},
			"properties": {
				"title": "路线一",
				"kind": 1
			}
		}
	]
}

2. set buffer to 0
   

3. the point of this triangle will lost in particular level