* lib/rubygems:  Update to RubyGems master 278d00d.  Changes:

  Fixes building extensions without a "clean" make rule

  Adds gem dependency file autodetection to "gem install -g"

* test/rubygems:  Tests for the above.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43299 b2dd03c8-39d4-4d8f-98ff-823fe69b080e