Fix temp-interrupt with LIN_ADVANCE

[AnHardt]

Error mechanism: Let's suppose we are in 'Temperature::isr()'.

  CBI(TIMSK0, OCIE0B); //Disable Temperature ISR
  sei();

The temperature-interrupt is disabled, but all others are enabled.

Now the temp-isr is interrupted by the Stepper::advance_isr_scheduler()

    // Disable Timer0 ISRs and enable global ISR again to capture UART events (incoming chars)
    CBI(TIMSK0, OCIE0B); // Temperature ISR
    DISABLE_STEPPER_DRIVER_INTERRUPT();
    sei();

temp-isr and stepper-isr are disabled. When we leave the Stepper::advance_isr_scheduler() we execute

    // Restore original ISR settings
    cli();
    SBI(TIMSK0, OCIE0B);
    ENABLE_STEPPER_DRIVER_INTERRUPT();

Enable temp-isr and stepper-isr. In case we interrupted the temp-isr this does not restore the ISR settings, but enables the temp-isr falsely. If its time for a fresh temp-isr now, this is entered before the still on the stack temp-isr ended - the temp-isr bites its tail.

Problems: Is temp-isr is entered multiple times the stack may overflow. temp-isr is not made for reentering.

Symptoms: Sampling OVERSAMPLENR+1 (or more) instead of OVERSAMPLENR samples.

• if the temperature is low (high raw values) this may result in min-temp-error.
• if the temperature is high it looks like a sudden, and only one time, drop of temperature by about 1/17 the expected one.

Even worse and unpredictable things when the stack overfolowes