[locale] Prefer non-empty country matches

Prefer "en_US" over "en" even when asking for "en".

src/modules/locale/LocaleNames.cpp

@@ -84,7 +84,7 @@ LocaleNameParts::similarity( const LocaleNameParts& other ) const
         return 0;
     }
     const auto matched_region = ( region == other.region ? 30 : 0 );
-    const auto matched_country = ( country == other.country ? 20 : 0 );
+    const auto matched_country = ( country == other.country ? ( country.isEmpty() ? 10 : 20 ) : 0 );
     const auto no_other_country_given = ( ( country != other.country && other.country.isEmpty() ) ? 10 : 0 );
     return 50 + matched_region + matched_country + no_other_country_given;
 }