The Men's Central Jail in downtown Los Angeles is, by any measure, a daunting place. It's in bad physical condition and perennially overcrowded. There are gang fights, beatings and sexual assaults. Many of the inmates are either drug addicts, mentally ill, or both. So the Board of Supervisors this week unanimously passed a resolution to study tearing down part of the jail and building a new facility just for the mentally ill. The idea is that by giving those inmates special attention, they will have a better chance at rehabilitation; and the Supervisors hope that would eventually save the county money.