Fix missing #include of <memory>

Change-Id: I11a4e232305e3866ed418a65041aa87ce385c071

internal/ceres/program.h

diff --git a/internal/ceres/program.h b/internal/ceres/program.h
index dc544c2..dd5f6e1 100644
--- a/internal/ceres/program.h
+++ b/internal/ceres/program.h
@@ -31,6 +31,7 @@
 #ifndef CERES_INTERNAL_PROGRAM_H_
 #define CERES_INTERNAL_PROGRAM_H_
 
+#include <memory>
 #include <set>
 #include <string>
 #include <vector>