Benewake, LeddarOne, LightWareSerial, MAVLink, MaxsonarI2CXL, MaxsonarSerialLV, NMEA, PX4_PWM, uLanding and Wasp already stored the last read time so for these drivers, this change just moves that storage to the state structure
analog, BBB_PRU, Bebop, LightWareI2C, PulsedLightLRF, TeraRangerI2C, VL53L0X did not store the last read time so this was added
- uart->available(); returns uint32 but was stored locally as int32 and treated as uint32. Now stored correctly as uint32
- some variables were set to zero at start of function, then reset to zero before being used. wasted work
Having a critical divide by value as a class member that could change external to the function using it is fragile. It was not very obvious that a divide by zero was not possible in the current design, now it's very obvious and safer in case the code changes later.