Generalisation module: coastlines #2408

Currently coastline processing is done with the separate program OSMCoastline or the data is simply downloaded from osmdata.openstreetmap.de. osm2pgsql should eventually be able to process coastlines directly from OSM data. With the new generalization framework that might just be possible.

Any solution must be able to cope with the problem that the coastline is often broken somewhere on the planet creating invalid data. That’s why this is somewhat tricky and not just a case of merging all ways tagged natural=coastline and creating polygons from that.