Provide Jet Eigen::NumTraits quiet_NaN and infinity

The definitions are required by Eigen::SelfAdjointEigenSolver.

Change-Id: Ifcc3348b381d9116e6cb3e2d3ec47c7450c3382a

include/ceres/jet.h

diff --git a/include/ceres/jet.h b/include/ceres/jet.h
index 3b7f23f..3672011 100644
--- a/include/ceres/jet.h
+++ b/include/ceres/jet.h
@@ -1433,6 +1433,14 @@
     return Real(std::numeric_limits<T>::epsilon());
   }
 
+  static inline Real quiet_NaN() {
+    return Real(std::numeric_limits<T>::quiet_NaN());
+  }
+
+  static inline Real infinity() {
+    return Real(std::numeric_limits<T>::infinity());
+  }
+
   static inline int digits10() { return NumTraits<T>::digits10(); }
   static inline int max_digits10() { return NumTraits<T>::max_digits10(); }