DNS_RDATA_UPDATE flag.
531. [func] Rdata really should be initalized before being
assigned to (dns_rdata_fromwire(), dns_rdata_fromtext(),
dns_rdata_clone(), dns_rdata_fromregion()),
check that it is.
hidden behind #ifdef's, since no OPT code number has yet to be assigned
by the IANA. They are also not quite complete in all regards; VIEW
options are understood and ignored. ZONE options are understood and
acted upon, though some of the error cases aren't quite right.
Remove doubled isc_mem_stats in dighost.c
Update todo list.
Change literal 255's to DNS_NAME_MAXWIRE in name.c
