gcd: use lowestOneBit, change to iterative. lcm: to multiply after divide.
gcd: use lowestOneBit, change to iterative. lcm: to multiply after divide.

peterolson/BigInteger.js,Yaffle/BigInteger.js,peterolson/BigInteger.js,Yaffle/BigInteger.js,peterolson/BigInteger.js,SleipnirFr/BigInteger.js,Yaffle/BigInteger.js,SleipnirFr/BigInteger.js