CRAWFORD, Texas (Reuters) - President Bush signed into law Saturday a measure aimed at saving U.S. companies more than $80 billion in pension contributions over two years, days before many firms make quarterly payments. Businesses lobbied hard for the bill, which would provide about $80 billion in pension accounting relief through the end of 2005 for some 31,000 companies with traditional "defined benefit" pension plans. Those cover about 35 million workers and promise a specific payout based on salary and service. Many traditional pension plans are underfunded because of the weak stock market the last few years and current low...