Fix boost::get usage for boost v1.58
Fix boost::get usage for boost v1.58

cyberpepe/pepecoin-core,memeticproject/memetic-core,memeticproject/memetic-core,cyberpepe/pepecoin-core,cyberpepe/pepecoin-core,memeticproject/memetic-core,cyberpepe/pepecoin-core,cyberpepe/pepecoin-core,memeticproject/memetic-core,memeticproject/memetic-core,memeticproject/memetic-core,cyberpepe/pepecoin-core