Proposal to remove COAP_MEDIATYPE_ANY

[obgm]

COAP_MEDIATYPE_ANY has been defined as 0xff in the very early implementation phase of libcoap (i.e., mid 2010) to gain a bit of flexibility with media type handling (what later has become Content-Format in RFC 7252). It was originally intended to mimic the HTTP Accept: * but the CoAP Accept option then was defined to work in a different way. A major issue with this definition is that the value 255 is in no way special and therefore in principle is open for IANA registration. Since COAP_MEDIATYPE_ANY is not used in the libcoap core and most likely not in applications as there is little use of this in the public libcoap API, my feeling is that this definition should be removed. (In theory, any value above 64999 would do, even, e.g., 0x1ffff but keeping unused code clutters the API).

[mrdeep1]

Given that if the CoAP Accept Option is not present in the request, this indicates 'Any' (Accept) there is no need for the non-standard COAP_MEDIATYPE_ANY (unlikely to be recognized by any other CoAP implementation) to be used in an Accept Option.

I have no issues with it being deleted.