It took 30 minutes for a homeless man to pilfer pills and two bottles of shampoo from the pockets and bags of a fellow vagrant who had dropped dead at the Downtown Crossing T station early yesterday morning.Police later collared Anthony Stimson, 30, blocks away with a bottle of 22 Gabapentin pills bearing the prescribed name of Willie Williams, the 52-year-old homeless man pronounced dead at 5:13 a.m. on the southbound platform for the Orange Line.