Reapply #167
Reapply #167

vks/num,rust-num/num-traits,koverstreet/num,rust-lang/num,rust-num/num-bigint,DonSheddow/num,rust-num/num-integer,rust-num/num-traits,rust-lang/num,rust-num/num-integer,DonSheddow/num,rust-num/num,rust-num/num,vks/num,koverstreet/num,rust-num/num-bigint