Not every MCU offers open drain pins, but some do. This changemeans that they'll no longer have to play games to implement anAPI-compatible pinMode() function that offers open drain.Fixesarduino#155If you're reading this commit message because you need to add anotherpin mode to this enum, the hacky trivial workaround is to do somethinglike this in your core:```// This typedef is used to extend the PinMode typedef enum// in the ArduinoAPI, since they don't have contantstypedef enum {        INPUT_ANALOG = 99 , // We assume that the Arduino core will never have 99 PinModes        OUTPUT_OPEN_DRAIN   // It'd be cleaner to be able to count the size of that enum} PinModeExtension;```Because PinMode is an enum and not a proper type, the compiler willlet the user pass either a PinMode or a PinModeExtension to yourpinMode() function, even though the signature is`void pinMode(pin_size_t ulPin, PinMode ulMode)`