.. and enable it on atmel-samd and raspberrypi. On trinket_m0 this saves
96 net bytes of flash. There are 216 bytes actually saved by reducing
the flash storage size of the property descriptors, but added code in
several paths takes back over half of the 'raw savings'.
By organizing the "get-only" and "get-set" (but no delete) properties
each in a different section, we can represent then more efficiently.
Testing performed: that a get-only property can still be gotten but
can't be set or deleted; that a get-set property can sill be gotten or
set but can't be deleted. Tested on pygamer.
Because this requires linker file support, I only enabled it on two of
the ports.
Tested & working:
* Send standard packets
* Receive standard packets (1 FIFO, no filter)
Interoperation between SAM E54 Xplained running this tree and
MicroPython running on STM32F405 Feather with an external
transceiver was also tested.
Many other aspects of a full implementation are not yet present,
such as error detection and recovery.
