Doing business in Burma has often cost American companies p.r. points: Pepsi, Apple Computer and Levi Strauss are just a few of the U.S. firms that pulled out of the military-ruled state after being pressured by human-rights groups. Now, however, doing business with regimes like the one in Rangoon may cost American companies cash as well as goodwill. Last week...Unocal chose to settle a landmark lawsuit...[also refers to Total]