Match type of arguments to min() and max()

[per1234]

max() and min() were changed from macros to templates in ESP8266 core for Arduino 2.4.0. This change causes calls to these functions with arguments of different types to cause a compilation error "error: no matching function for call to". This commit changes the arguments to these functions to the same type to fix compatibility with ESP8266.

[gyssels]

@per1234 @anselmpaul I will accept PR on gyssels/Arduino-CmdMessenger, and I messaging the other PR submitters so it can become an active branch I engage myself to do a full PR back here if in the future I'll not maintain this anymore.