* lib/rubygems/commands/cleanup_command.rb:  Clean all possible gems
  using multiple passes.  Fixes RubyGems bug #422.  Refactored for
  maintainability.
* test/rubygems/test_gem_commands_cleanup_command.rb:  Test for above.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38698 b2dd03c8-39d4-4d8f-98ff-823fe69b080e