Boston’s Big Dig is legendary — for its politics, cost overruns and rage-inducing traffic snarls. But most Bostonians don’t remember that the project emerged from an anti-highway movement that was resisting the nation’s newfound love of interstates. Discover more tidbits about this megaproject with Ian Coss, lead producer and host of “The Big Dig,” a new podcast from GBH News and PRX.