In a large deep saucepan bring neck, giblets, broth, water, celery, carrot, and onion to a boil, skimming froth. Add remaining ingredients and cook, uncovered at a bare simmer 2 hours, or until liquid is reduced to about 6 cups. Pour stock through a fine sieve into a bowl. Stock may be made 2 days ahead. Cool stock completely, uncovered, and keep chilled or frozen in an airtight container.