Backing Clinton, Democrats to flag Trump's 'dangerous' approach

By Amanda Becker and Jeff Mason PHILADELPHIA/WASHINGTON (Reuters) - President Barack Obama will paint an optimistic picture of America's future and give full-hearted support to Hillary Clinton in a speech on Wednesday to help her become the first woman elected U.S. president and stop Republican Donald Trump. On a day when Democrats meeting at their convention in Philadelphia planned to tout their candidate as far better suited than Trump to keep the country safe, the Republican gave his critics