As reported by Michael Kussmaul on dev list osm2pgsql does not calculate small
way_areas properly. This patch fixes this by replacing "%f" by "%g".

Also requested by Michael this patch adds a way to disable the output
of a generated way_area tag alltogether by using a delete statement
in the style.



git-svn-id: http://svn.openstreetmap.org/applications/utils/export/osm2pgsql@29443 b9d5c4c9-76e1-0310-9c85-f3177eceb1e4