Add VM test for primitiveStringNextIndexOfFromTo
Add VM test for primitiveStringNextIndexOfFromTo

dolphinsmalltalk/Dolphin,blairmcg/Dolphin,jgfoster/Dolphin,blairmcg/Dolphin,dolphinsmalltalk/Dolphin,jgfoster/Dolphin,objectarts/Dolphin,blairmcg/Dolphin,dolphinsmalltalk/Dolphin,shoshanatech/Dolphin,jgfoster/Dolphin,shoshanatech/Dolphin,shoshanatech/Dolphin,jgfoster/Dolphin,shoshanatech/Dolphin,blairmcg/Dolphin,dolphinsmalltalk/Dolphin,objectarts/Dolphin