Add Nano V2 specific board define to library compiles to fix the WStream Incompatibility

[drmpf]

The Arduino support for Nano V2 is not compatiable with Arduino Stream. The Nano V2 replaces the Arduino Stream with WStream while calls to Stream pick up the incompatible mbed::Stream This breaks standard libraries.

One solution is to add the following

#if defined( ARDUINO_RBL_nRF52832)
  #include <WStream.h>
  #define Stream WStream
#else
  #include <Stream.h>
#endif

But this does not work because ARDUINO_RBL_nRF52832 is only defined when detecting libraries and is not defined when compiling included libraries via the Arduino IDE Please make a board specific define available that is defined only for this board and defined for ALL compilations.

[drmpf]

Note for Nano V1.5 ARDUINO_RBL_nRF51822 is defined for both detecting libraries and for compiling libraries