HARRISBURG, Pennsylvania (Reuters) - Pennsylvania became the fifth U.S. state to seek universal health coverage for its citizens on Wednesday when it unveiled a plan to provide medical insurance for some three-quarters of a million residents who currently have none. Along with other states including Massachusetts and California, Pennsylvania is joining a growing movement among U.S. states to tackle the problem of residents without health care insurance, which according to some estimates number as many as 46 million Americans or about 15 percent of the population. The problem of uninsured medical costs, often left to be covered at taxpayer expense,...