Gov. Patrick J. Quinn signed a new law over the weekend that will allow children to use medical marijuana to treat certain ailments, and he enacted another law to help job applicants with criminal records avoid some bias over their backgrounds. Senate Bill 2636 amends the broader medical cannabis law, which was passed and signed last year, to permit children under 18 to use medical marijuana if they are suffering from certain ailments. The list of serious diseases that can be legally treated with marijuana includes …