Add NumTraits::max_digits10 for Jets

Change-Id: Ief2c02eeaefba98d2540eb2f3428c65a98e36ef5

include/ceres/jet.h

diff --git a/include/ceres/jet.h b/include/ceres/jet.h
index d6b8688..7f9f5be 100644
--- a/include/ceres/jet.h
+++ b/include/ceres/jet.h
@@ -1381,6 +1381,7 @@
   }
 
   static inline int digits10() { return NumTraits<T>::digits10(); }
+  static inline int max_digits10() { return NumTraits<T>::max_digits10(); }
 
   enum {
     IsComplex = 0,