binary-search: use nth-unsafe for a further performance gain
binary-search: use nth-unsafe for a further performance gain

bpollack/factor,bjourne/factor,sarvex/factor-lang,sarvex/factor-lang,bpollack/factor,AlexIljin/factor,mrjbq7/factor,tgunr/factor,nicolas-p/factor,factor/factor,factor/factor,dch/factor,bpollack/factor,AlexIljin/factor,nicolas-p/factor,sarvex/factor-lang,AlexIljin/factor,mrjbq7/factor,tgunr/factor,slavapestov/factor,AlexIljin/factor,factor/factor,sarvex/factor-lang,tgunr/factor,slavapestov/factor,dch/factor,bjourne/factor,mrjbq7/factor,factor/factor,bpollack/factor,bjourne/factor,dch/factor,slavapestov/factor,sarvex/factor-lang,nicolas-p/factor,nicolas-p/factor,tgunr/factor,sarvex/factor-lang,nicolas-p/factor,sarvex/factor-lang,nicolas-p/factor,factor/factor,tgunr/factor,AlexIljin/factor,bpollack/factor,AlexIljin/factor,nicolas-p/factor,slavapestov/factor,bpollack/factor,AlexIljin/factor,factor/factor,slavapestov/factor,mrjbq7/factor,bjourne/factor,bjourne/factor,bjourne/factor,dch/factor,tgunr/factor,bpollack/factor,mrjbq7/factor,dch/factor,dch/factor,mrjbq7/factor,slavapestov/factor,bjourne/factor,slavapestov/factor