in the Compute() function, timeChange is now declared as "unsigned long"

formerly, if left in manual mode for a long time (e.g. during an autotune,)
 the "int" timeChange would wrap causeing the PID not to calculate for an
unacceptable period of time.

PID_v1/PID_v1.cpp

@@ -46,7 +46,7 @@ void PID::Compute()
 {
    if(!inAuto) return;
    unsigned long now = millis();
-   int timeChange = (now - lastTime);
+   unsigned long timeChange = (now - lastTime);
    if(timeChange>=SampleTime)
    {
       /*Compute all the working error variables*/