instance variables when it is referenced multiple times.
* ext/psych/lib/psych.rb: bump version
* ext/psych/psych.gemspec: bump version
* test/psych/test_hash.rb: test for fix
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49432 b2dd03c8-39d4-4d8f-98ff-823fe69b080e