High-end US jeweler Tiffany & Co. reported a higher-than-expected profit and raised its full-year forecast, while Zale Corp reported a loss caused by price markdowns.   Tiffany & Co. doubled its second-quarter net profit to $80 million, compared with $40 million a year earlier.  Sales increased 11 percent to $734 million due to strong growth in the Asian-Pacific and European regions.