Modified speed calculation for slow speeds

Calculates the upper limit of the speed based on the time elapsed since
the last speed_change event.
If this upper limit is slower than the last real measurement, this
slower speed is used.

Author: jenkie

Arduino_Pedelec_Controller/Arduino_Pedelec_Controller.ino

@@ -635,6 +635,11 @@ void loop()
         spd=1;
     }
 
+//live speed update when there is no speed_change interrupt-----------------------------------------------------------------
+    long wheeltime_temp=(millis()-last_wheel_time)*wheel_magnets; //current upper limit of the speed based on last measurement
+    if (wheeltime_temp>wheel_time)                                //is current upper limit slower than last real measurement?
+      spd = 3600*wheel_circumference/wheeltime_temp;
+
 //Power control-------------------------------------------------------------------------------------------------------------
     power_throttle = throttle_stat / 1023.0 * curr_power_max;         //power currently set by throttle