By Natalia Zinets LVIV, Ukraine (Reuters) -Nearly 5,000 people, including about 210 children, have been killed in the southern Ukrainian city of Mariupol since Russian forces laid siege to it, a spokesperson for the mayor said on Monday. It was not immediately clear how Mayor Vadym Boichenko had calculated the toll from a month of Russian bombardment that has devastated the city and trapped tens of thousands of residents without power and with few supplies. Boichenko’s office said 90% of Mariupol’s buildings had been damaged and 40% destroyed, including hospitals, schools, kindergartens and fa…