Create tag handlers (including child tags) and a geodata class for KML NetworkLinkControl. See https://developers.google.com/kml/documentation/kmlreference#networklinkcontrol

In the networklinkcontrol tag handler, check that it's a child of kml (parentItem.qualifiedName().first == kmlTag_kml) and only then set a new networklinkcontrol to the document (GeoDataDocument* doc = geoDataDoc( parser );). Extend GeoDataDocument by a getter/setter for networklinkcontrol.

Add a test case TestNetworkLinkControl.cpp similar to the other test cases which tests successful parsing.