Add missing algorithm header to manifold.cc

Change-Id: I6211c65658ee124fc6a6587923e3ceadca76e24a

internal/ceres/manifold.cc

diff --git a/internal/ceres/manifold.cc b/internal/ceres/manifold.cc
index 365d5d6..dc88302 100644
--- a/internal/ceres/manifold.cc
+++ b/internal/ceres/manifold.cc
@@ -1,5 +1,6 @@
 #include "ceres/manifold.h"
 
+#include <algorithm>
 #include <cmath>
 
 #include "ceres/internal/eigen.h"