8224174: java.lang.Number has a default constructor

Reviewed-by: rriggs, bpb

src/java.base/share/classes/java/lang/Number.java

@@ -53,6 +53,11 @@ package java.lang;
  * @since   1.0
  */
 public abstract class Number implements java.io.Serializable {
+    /**
+     * Constructor for subclasses to call.
+     */
+    public Number() {super();}
+
     /**
      * Returns the value of the specified number as an {@code int}.
      *