rangetree: support for building on freebsd-10

extern/rangetree/range_tree.hh

@@ -35,6 +35,11 @@ struct RangeTree {
 			: min(t), max(t), single(true)
 		{}
 
+		Range& operator=(const Range& v) {
+			*this = v;
+			return *this;
+		}
+
 		bool operator<(const Range& v) const {
 			return max < v.min;
 		}