Fix delay()

[ebuehrle]

Calling delay(0) would unexpectedly block for a while. This fixes the issue.

[MCUdude]

Thanks! But why would you call delay(0)?

[per1234]

You might find this in code that is written to be cross-platform with ESP8266, where it is one way to reset the watchdog:
https://arduino-esp8266.readthedocs.io/en/2.7.4_a/reference.html#timing-and-delays

[ebuehrle]

Exactly @per1234. By the way, thank you for this great library, @MCUdude.