lib: Slightly improved accuracy estimates
lib: Slightly improved accuracy estimates

When I added these:

1. For city, I was thinking of diameter rather than radius.
2. For country, I did some miscalculations as 150 km is too small.

https://bugzilla.gnome.org/show_bug.cgi?id=697962

mlundblad/geocode-glib,Distrotech/geocode-glib,Distrotech/geocode-glib,mlundblad/geocode-glib,mlundblad/geocode-glib