Care for version - timestamp contradictions on elements

[drolbr]

There is at least one element,
http://www.openstreetmap.org/api/0.6/node/1336722067/history
that has two versions at the exactly same timestamp.

This causes somewhat undefined behaviour for attic data of this element. A better solution would be to keep only the younger element and drop the older version.

More difficult is the case of higher versions with older timestamp. AFAIK this has not been observed in the wild, but it is unclear what should happen then.

[drolbr]

This is now superseded by issue #346 .