deprecate delegation-only and root-delegation only

deprecate delegation-only and root-delegation only

These options and zone type were created to address the
SiteFinder controversy, in which certain TLD's redirected queries
rather than returning NXDOMAIN. since TLD's are now DNSSEC-signed,
this is no longer likely to be a problem.

The deprecation message for 'type delegation-only' is issued from
the configuration checker rather than the parser. therefore,
isccfg_check_namedconf() has been modified to take a 'nodeprecate'
parameter to suppress the warning when named-checkconf is used with
the command-line option to ignore warnings on deprecated options (-i).