France's socialist government has declared a three-year tax holiday for newly formed companies and a two-year exemption from personal taxes for employees who leave one company to form another. And the government has told banks to make some $1 billion in relatively cheap corporate loans this year -- and to give small and medium-size companies preferential treatment. Not coincidentally, France's love affair with small business is blossoming as its marriage to nationalized big business appears headed for the rocks. In 1981 and '82, the government nationalized six large industrial groups and then flooded them with subsidies. The result five of the six had heavy losses in 1982 with more of the same expected in '83.