Add a missing include

Change-Id: I0a3fa842183bc7cb9ba00b17d6181cebc3eac50d

internal/ceres/program_evaluator.h

diff --git a/internal/ceres/program_evaluator.h b/internal/ceres/program_evaluator.h
index da225dc..a9bd65a 100644
--- a/internal/ceres/program_evaluator.h
+++ b/internal/ceres/program_evaluator.h
@@ -94,6 +94,7 @@
 
 #include "absl/log/log.h"
 #include "ceres/evaluation_callback.h"
+#include "ceres/evaluator.h"
 #include "ceres/execution_summary.h"
 #include "ceres/internal/eigen.h"
 #include "ceres/parallel_for.h"