I'm David Colman, and I'm an alcoholic. In the 15 years since I quit drinking, I've neither spoken nor written those words, and now, in doing so, I have more or less violated the first-name-only tenet of Alcoholics Anonymous, the grass-roots organization whose meetings have helped me (and millions of others) quit drinking. As A.A.'s 11th Tradition states, ''We need always maintain personal anonymity at the level of press, radio and films.''