Remove trailing whitespace
Import ruby trunk r43772

> don't call gem method if Test::Unit is defined
>
> ruby's test-all may define 'gem' method somewhere,
> and it cause test failure.
Import ruby trunk r43725

> test_rdoc_generator_darkfish.rb: ignore nlink is not provided
>
> * test/rdoc/test_rdoc_generator_darkfish.rb (assert_hard_link): makes
>   no sense on platforms where link count is not provided.