The Illinois Supreme Court struck down the state’s 2013 pension overhaul, unraveling an effort by lawmakers to rein in benefits for the consistently underfunded public-sector system. The current pension shortfall is estimated at $111 billion, one of the largest nationally. The high court affirmed a decision in November by a state circuit court that the legislative changes violated pension protections written into the state constitution. The decision is a victory for a consortium of public-sector unions while creating a huge challenge for new Republican Gov. Bruce Rauner, who already faces a yawning budget deficit for the coming fiscal year.