Ruby » Ruby master

• lib/irb/magic-file.rb: set a encoding, which is detected from
  the file to read, to the internal encoding.
  [Bug #4281][ruby-dev:43036]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38285 b2dd03c8-39d4-4d8f-98ff-823fe69b080e