rails/rails — pull request #6583 by amatsuda (2012-06-01 07:52:48+00:00)
Title: Revert "Only include Rake::DSL if it's defined."

Because Ruby >= 1.9.3 is shipped with Rake > 0.9

```
% ruby -v -rrake -e 'p defined? Rake::DSL'
ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin11.1.0]
"constant"
```