Minor bug fixes

Change-Id: I94e4521adf76a6c77db954c4a8955168e9d37b55
diff --git a/internal/ceres/iterative_schur_complement_solver.cc b/internal/ceres/iterative_schur_complement_solver.cc
index 9a66c1e..c44bd39 100644
--- a/internal/ceres/iterative_schur_complement_solver.cc
+++ b/internal/ceres/iterative_schur_complement_solver.cc
@@ -42,6 +42,7 @@
 #include "ceres/internal/eigen.h"
 #include "ceres/internal/scoped_ptr.h"
 #include "ceres/linear_solver.h"
+#include "ceres/preconditioner.h"
 #include "ceres/schur_jacobi_preconditioner.h"
 #include "ceres/triplet_sparse_matrix.h"
 #include "ceres/types.h"