Make Stump::predict const

modules/xobjdetect/include/opencv2/xobjdetect.hpp

@@ -147,7 +147,7 @@ public:
 
     Returns real value, sign(value) means class
     */
-    float predict(int value);
+    float predict(int value) const;
 
 private:
     /* Stump decision threshold */

modules/xobjdetect/src/stump.cpp

@@ -196,7 +196,7 @@ int Stump::train(const Mat& data, const Mat& labels, const Mat& weights)
     return min_row;
 }
 
-float Stump::predict(int value)
+float Stump::predict(int value) const
 {
     return polarity_ * (value - threshold_) > 0 ? pos_value_ : neg_value_;
 }