* bignum.c (nlz16): New function.
  (nlz32): Ditto.
  (nlz64): Ditto.
  (nlz128): Ditto.
  (nlz): Redefined using an above function.
  (bitsize): New macro.
  (rb_cstr_to_inum): Use bitsize instead of nlz.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41716 b2dd03c8-39d4-4d8f-98ff-823fe69b080e