old ChangeLog and NEWS move to doc

* doc/NEWS-2.1.0: moved from NEWS
* doc/ChangeLog-2.1.0: moved ChangeLog older than created ruby_2_0_0 branch
* NEWS: NEWS for 2.2.0 that describes changes since 2.1.0
* ChangeLog: ChangeLog since created v2_1_0_rc1 tag (branch point of ruby_2_1 branch)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44427 b2dd03c8-39d4-4d8f-98ff-823fe69b080e