handle rounding problems in PolygonDescProcessor

Make sure that nodes on the polygon ways are rounded to grid
points and that equal latitude or longitude values in the OSM nodes 
are rounded to the same grid values, so that rectilinear shapes
are kept.


git-svn-id: http://svn.mkgmap.org.uk/splitter/trunk@334 838fabe5-b1a8-4b81-9896-7a84386980e9
fix build: pass resolution parameter

git-svn-id: http://svn.mkgmap.org.uk/splitter/trunk@335 838fabe5-b1a8-4b81-9896-7a84386980e9