* lib/rubygems:  Update to RubyGems master 3de7e0f.  Changes:

  Only attempt to build extensions for newly-installed gems.  This
  prevents compilation attempts at gem activation time for gems that
  already have extensions built.

  Fix crash in the dependency resolver for dependencies that cannot be
  resolved.

* test/rubygems:  ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43368 b2dd03c8-39d4-4d8f-98ff-823fe69b080e