Add the min_increment function for use by libscatter

include/9float.hpp

@@ -34,7 +34,12 @@ public:
     : backend{0}
     {}
 
-
+    constexpr static Q min_increment()
+    {
+        Q n;
+        n.backend = 1;
+        return n;
+    }
 
     constexpr bool is_negative()
     {