BREAKING: empty nodes in returned xml are self-closing
BREAKING: empty nodes in returned xml are self-closing

The OSM XML examples use self-closing tags: http://wiki.openstreetmap.org/wiki/OSM_XML
Previously osm-p2p-xml returned empty tags instead of self-closing tags
e.g. `<node  lat="111" lon="222" id="1"></node>` vs `<node  lat="111" lon="222" id="1"/>`
This should not cause an issue for most users.

substack/osm-p2p-server,digidem/osm-p2p-server