* file.c: [DOC] document File.join returns a string.
  Contributed by @dapplebeforedawn. [fix GH-646]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46620 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-06-30

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46621 b2dd03c8-39d4-4d8f-98ff-823fe69b080e