By Kareem Raheem BAGHDAD (Reuters) - A suicide bomber killed 15 people as they left a Shi'ite mosque in the Iraqi capital on Friday and a separate attack on Sunni protesters killed seven, police and medics said. In Baghdad's northwestern district of Graiaat, witnesses said guards at the exit to the Shi'ite mosque stopped a woman who then blew herself up amidst worshippers leaving after sunset prayers. Suicide bombings are the hallmark of al Qaeda. ...