clean up some deprecated/obsolete options and doc
- removed documentation of -S option from named man page
- removed documentation of reserved-sockets from ARM
- simplified documentation of dnssec-secure-to-insecure - it now just says it's obsolete rather than describing what it doesn't do anymore
- marked three formerly obsolete options as ancient: parent-registration-delay, reserved-sockets, and suppress-initial-notify
Closes #3780 (closed)