MEXICO CITY (Reuters) -Mexican journalists on Tuesday started nationwide protests to denounce the recent murders of three reporters, demanding an end to impunity that has often characterized the killings of their colleagues. The protests follow the murder of seasoned journalist Lourdes Maldonado on Sunday, some three years after she raised the issue of killings with President Andres Manuel Lopez Obrador and said she feared for her life. Protesters in the central state of Puebla laid flowers and candles on the street along with signs that read “I’m angry at censorship”, television footage showe…