histogram: Add missing #include.

Commit 02b9b37698eb "Disable asserts in histogram code except in
--testing-mode" added a use of settings_get_testing_mode() but didn't
include the proper header.  This fixes the problem.

diff --git a/src/math/histogram.c b/src/math/histogram.c
index 51916a3d8baef7649f1920d6c2635c90a36824a1..b00067210f08676736d589660c9eb85f75216831 100644 (file)
--- a/src/math/histogram.c
+++ b/src/math/histogram.c
@@ -21,6 +21,7 @@
 #include <gsl/gsl_histogram.h>
 #include <math.h>
 
+#include "data/settings.h"
 #include "libpspp/message.h"
 #include "libpspp/assertion.h"
 #include "libpspp/cast.h"