By Patricia Zengerle WASHINGTON (Reuters) - The Republican takeover of the U.S. Senate will bring a tough new tone to the debate over Washington's foreign policy, with lawmakers expected use their new clout and Power over the budget to promote a more interventionist foreign policy. While leaders of the Democratic-majority Senate mostly backed President Barack Obama's international goals, Republicans plan to pressure the White House to take a tougher line on Iran, Russia and Islamic State fighters in Iraq and Syria. ...