Feature enc x24 j600 wip

- Adding classes Register_GPIO_BSRRL & Register_GPIO_BSRRH and modifying GPIO.h
- Adding objects for Register_GPIO_BSRRL & Register_GPIO_BSRRH in emulator.mk
- Now, all the RF tests works fine with ellduino, stm32f4discovery & stm32f334nucleo
They are not needed, but I want to preserve them.  Also, I did *NOT* remove them from system_init.h.  That's one of the places where I edited your previous pull request.