Replace hard-coded values with enums and explicit manage all enumeration
values in CO_process_SYNC() to avoid warnings like this:
CANopen.c:837:5: warning: enumeration value ‘CO_SYNC_NONE’ not handled in switch [-Wswitch]
837 | switch (sync_process) {
| ^~~~~~
* Merge two parts of CO_PDO_receive() into single common code
* Add CO_RPDO_initCallbackPre() for received RPDO messages
This optional mechanism allows to immediatelly wake the thread that
processes RPDO, without waiting for its next tick.
* Add CO_SYNC_initCallbackPre() for received SYNC messages
This optional mechanism allows to immediatelly wake the thread that
processes SYNC, without waiting for its next tick.
