test cases don't handle loops

[ghost]

I hand crafted a gpx for testing and got some test errors from the simplify_polyline call. The track that I made was a loop and had the same exact start point and end point. I don't think it is against the spec to have such a track, and it is almost impossible to have such a track in real life, but I thought I'd bring it up anyway in case you wanted to fix that corner case.

[tkrajina]

You are right, again!

Should be OK after this: 6054863

Thanks!