[mkgmap-dev] [PATCH v1] - handle "anti-islands"

This patch extends the sea generation stuff to cope with anti-islands (water inside, land outside and, presumably, where the anti-treasure is hidden). Anti-islands are tagged natural=water (you can't use natural=sea because it will be beneath the surrounding land polygon). Note that if your map contains any islands whose direction is incorrect, they will now be filled with water. To help find such islands, a warning message is output when an anti-island is discovered. The upside is that if your map contains anti-islands whose direction is correct, they will now become visible. Mark