old ChangeLog and NEWS move to doc

* doc/NEWS-2.0.0: moved from NEWS
* doc/ChangeLog-2.0.0: moved ChangeLog older than created ruby_2_0_0 branch
* NEWS: NEWS for 2.1.0 that describes changes since 2.0.0
* ChangeLog: ChangeLog since created ruby_2_0_0 branch

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39479 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
fix major-mode for emacs

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39480 b2dd03c8-39d4-4d8f-98ff-823fe69b080e