Re-implement PWM generator logic

cores/esp8266/Tone.cpp

@@ -34,6 +34,11 @@ static void _startTone(uint8_t _pin, uint32_t high, uint32_t low, uint32_t durat
     return;
   }
 
+  // Stop any analogWrites (PWM) because they are a different generator
+  _stopPWM(_pin);
+  // If there's another Tone or startWaveform on this pin
+  // it will be changed on-the-fly (no need to stop it)
+
   pinMode(_pin, OUTPUT);
 
   high = std::max(high, (uint32_t)microsecondsToClockCycles(25));  // new 20KHz maximum tone frequency,