Add 'pop_allow_overpay' setting: set vai tariff-file if operpay is allowed.

library/include/mobilisis/payment_opt.h

@@ -42,6 +42,7 @@ public:
         pop_use_only_for_duration = 0;   // deprecated
         pop_plus_steps = 1;  // +: jump <x=1> steps forward
         pop_minus_steps = 1; // -: jump <x=1> steps backward
+        pop_allow_overpay = false;
     }
 
     int pop_id;
@@ -73,6 +74,7 @@ public:
     bool pop_accumulate_durations;
     int pop_plus_steps;
     int pop_minus_steps;
+    bool pop_allow_overpay;
 
     struct ATBMaxDateTime {
         int direction;