When you change this to true, you may need to add more tests.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53141 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
format for serializing nil values. Thanks Eric Hodel!
* test/psych/test_nil.rb: test for nil values
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@30459 b2dd03c8-39d4-4d8f-98ff-823fe69b080e