[mkgmap-dev] Added option to sanity check roundabout flare roads

As part of my current thrust to improve the mapping of the world's roundabouts, I have added an option that checks the sanity of roundabout flare roads. It probably can be fooled by some valid data but it's pretty good at finding bad roundabout flares. Specifically, it's looking for these errors: flare roads that point in the wrong direction flare roads that are not oneway flare roads that start or end beyond the "flare triangle" The UK map is very poor in this regard. I think I can do more to improve the routing in the UK now by just fixing the OSM data rather than working on mkgmap! You may want to enable this occasionally to help weed out the cruft in your maps. Mark