bbd2osm: protect against hash randomization

First part of the fixing: all $attribs are now tied using Tie::IxHash.
bbd2osm: protect against hash randomization

Second part of the fixing: stable sort order for multi-cityparts. This
is enough to get stable file output with the current BBBike data and
perl 5.18.2.
remove TODO_hash_randomization in bbbike-aux.t

bbd2osm has now stable output.
bbd2osm: the bbbike:landuse=industrial hack, err optimization