If it was nothing else the U.N. Special Session on Raw Materials and development, which stirred the East River enclave to an unwonted pitch of springtime activity last April, was a display of Third World solidarity. In spite of the massive balance-of-payments crisis threatening many of the less developed nations — a result of the sudden steep rise in the price of oil plus sharp increases in the prices of food and fertilizer — the atmosphere in the public forums reflected near euphoria because of the oil-producing (OPEC) nations' dramatic success in gaining control of their own natural resources.