[mkgmap-dev] [PATCH v2] Mp merge: generate-sea: bugfix for generate-sea=multipolygon

The flodded areas was a reason of the attitude of the mp code: mp does not recognize that polygon pi is in polygon po if they share a line or a point. The attached patch contains an easy workaround. The sea background area (which is the outer area in the mp) is increased by 1 so that it does not share any lines and points with any of the inner areas. WanMil