range.c: step in bignum
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63208 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
range.c: step in bignum
[Feature #12912]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63208 b2dd03c8-39d4-4d8f-98ff-823fe69b080e