Use new parse_..._panic functions from rustlang/rust#29285
Use new parse_..._panic functions from rustlang/rust#29285

birkenfeld/docopt.rs,brandonson/docopt.rs,birkenfeld/docopt.rs,zsiciarz/docopt.rs,zsiciarz/docopt.rs,birkenfeld/docopt.rs,brandonson/docopt.rs,brandonson/docopt.rs,zsiciarz/docopt.rs