TORONTO – The Canadian dollar hit the 80-cent US mark minutes after North American stock markets opened for trading today. The loonie was up 0.31 of a U.S. cent from Thursday's close of 79.69 cents US. The last time the loonie closed above that level was on June 30, 2015, when it settled at 80.06 cents US. The loonie's rise marks a remarkable turnaround in recent months for the currency, which has been aided by weakness in the U.S. dollar. In …