battery: use set_pin() to allow pins to be changed at runtime

ArduCopter/sensors.pde

@@ -78,10 +78,12 @@ static void read_battery(void)
 
     if(g.battery_monitoring == 3 || g.battery_monitoring == 4) {
         static AP_AnalogSource_Arduino batt_volt_pin(g.battery_volt_pin);
+        batt_volt_pin.set_pin(g.battery_volt_pin);
         battery_voltage1 = BATTERY_VOLTAGE(batt_volt_pin.read_average());
     }
     if(g.battery_monitoring == 4) {
         static AP_AnalogSource_Arduino batt_curr_pin(g.battery_curr_pin);
+        batt_curr_pin.set_pin(g.battery_curr_pin);
         current_amps1    = CURRENT_AMPS(batt_curr_pin.read_average());
         current_total1   += current_amps1 * 0.02778;            // called at 100ms on average, .0002778 is 1/3600 (conversion to hours)
     }

ArduPlane/sensors.pde

@@ -41,10 +41,14 @@ static void read_battery(void)
 
     if(g.battery_monitoring == 3 || g.battery_monitoring == 4) {
         static AP_AnalogSource_Arduino batt_volt_pin(g.battery_volt_pin);
+        // this copes with changing the pin at runtime
+        batt_volt_pin.set_pin(g.battery_volt_pin);
         battery_voltage1 = BATTERY_VOLTAGE(batt_volt_pin.read_average());
     }
     if(g.battery_monitoring == 4) {
         static AP_AnalogSource_Arduino batt_curr_pin(g.battery_curr_pin);
+        // this copes with changing the pin at runtime
+        batt_curr_pin.set_pin(g.battery_curr_pin);
         current_amps1    = CURRENT_AMPS(batt_curr_pin.read_average());
         current_total1   += current_amps1 * (float)delta_ms_medium_loop * 0.0002778;                                    // .0002778 is 1/3600 (conversion to hours)
     }