* doc/rubygems/*: Removed outdated documentation files
* lib/rubygems/LICENSE.txt: Include license file
* lib/rubygems.rb: Move Gem module documentation so rdoc can parse it
  and link to LICENSE.txt
* lib/rubygems/*: Hide useless documentation from Gem module rdoc


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39079 b2dd03c8-39d4-4d8f-98ff-823fe69b080e