[getdns-api] EDNS options are for server to server communications

[Willem Toorop]

EDNS0 options are for server to server communications. Therefore the
extensions that set them can only work in stub (i.e. target a specific
server) mode.

How about a GETDNS_RETURN_EDNS0_WITH_RECURSIVE_DISALLOWED return code?

-- Willem

PS.  Okay, except the maximum accepted udp_payload_size which is
configurable for a recursive too, but not on a per query basis...
Assigning the value to a context with the
getdns_context_set_edns_maximum_udp_payload_size is adequate for a
recursive...