Reorder includes. (#5749)

* Reorder includes.

* R.

src/common/quantile.h

@@ -7,14 +7,15 @@
 #ifndef XGBOOST_COMMON_QUANTILE_H_
 #define XGBOOST_COMMON_QUANTILE_H_
 
-#include <dmlc/base.h>
-#include <xgboost/logging.h>
 #include <cmath>
 #include <vector>
 #include <cstring>
 #include <algorithm>
 #include <iostream>
 
+#include <dmlc/base.h>
+#include <xgboost/logging.h>
+
 namespace xgboost {
 namespace common {
 /*!