RoadMerger always checks Coords for identity and not using equals() method

git-svn-id: http://svn.mkgmap.org.uk/mkgmap/trunk@2938 25d90789-57f7-4ee0-8453-03a3dfeeeb22
RoadMerger now preservers the original order of roads

This is done by keeping the index of roads and sorting it by this index after merging.

git-svn-id: http://svn.mkgmap.org.uk/mkgmap/trunk@2939 25d90789-57f7-4ee0-8453-03a3dfeeeb22