pdu.h: Added code for No-Response option
pdu.h: Added code for No-Response option

IANA has reserved 284 for No-Response, described in
http://www.iana.org/go/draft-tcs-coap-no-response-option

See also:
http://www.iana.org/assignments/core-parameters/core-parameters.xhtml#option-numbers

As a side-effect, COAP_MAX_OPT was set to 65535.

gebart/libcoap,authmillenon/libcoap,authmillenon/libcoap,gebart/libcoap,gebart/libcoap,authmillenon/libcoap