Child marriage became illegal in the Philippines on Thursday as a law banning the practice took effect in a country where one in six girls enters wedlock before the age of 18.The impoverished Southeast Asian country has the 12th-highest number of child marriages in the world, according to Britain-based rights group Plan International, with long-held cultural practices and gender inequality hindering change.But a new law, signed by President Rodrigo Duterte and released to the public on Thursday…