merges r22132 from trunk into ruby_1_9_1.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_1@22522 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merges r22132 from trunk into ruby_1_9_1.
a loop to fix iteration miss when hash is modified during iteration.
[ruby-dev:37910]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_1@22522 b2dd03c8-39d4-4d8f-98ff-823fe69b080e