* hash.c (rb_hash_recursive): make similar (recursive) constructs
return same hash value. execute recursively, and rewind to the
topmost frame with an object which .eql? to the recursive
object, if recursion is detected.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43981 b2dd03c8-39d4-4d8f-98ff-823fe69b080e