- nfc_device is now an opaque type;
- PN53x specific errors are not public anymore;
- nfc_device_name() renamed to nfc_device_get_name() for the sake of consistency;
- examples/*, utils/* uses the new nfc_device_get_name() function instead of access directly to struct's content;
- new error defined: NFC_ERFTRANS for notifying about RF transmission error, its used by mifare.c to detect permissions error on mifare;
- drivers initiator_transceive_bytes() function now returns libnfc's error code on failure (<0), and received bytes count on success (>=0);
- remove some unused errors.
