line options. [ruby-dev:37161]. Fixes #711.
  improved long optinos.

* lib/irb/init.rb (IRB.set_encoding): new subroutine for IRB.opt_parse

* lib/irb/input-method.rb (IRB::StdioInputMethod): (M17N) regards
  scripts that user types as encoded in the external_encoding.

* lib/irb/input-method.rb (IRB::ReadlineInputMethod): ditto.

* lib/irb/input-method.rb (IRB::FileInputMethod): (M17N) respects
  magic comment.

* lib/irb/help.rb (IRB.print_usage): (M17N) respects magic comment
  in the resource file.

* lib/irb/lc/help-message: adds -U and -E.

* lib/irb/lc/ja/help-message: ditto. re-encoded from ISO-2022-JP into UTF-8.

* lib/irb/lc/ja/encoding_aliases.rb: new file. provides Japanese specific
  character encoding name table for backward compatibility.

* lib/irb/lc/ja/error.rb: re-eoncoded from ISO-2022-JP into UTF-8.
  magic comment.

* lib/irb/locale.rb: integrated with Ruby 1.9's M17N support.

* lib/irb/magic-file.rb: new file. utility to handle files with magic
  comment and opens in the correct encoding.

* lib/irb/ruby-lex.rb (RubyLex#each_top_level_statement): recovers
  character encoding for a statement after it lexed so that irb can
  eval the statement in correct encoding.

* lib/irb/src_encoding.rb: new file. utility.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@20862 b2dd03c8-39d4-4d8f-98ff-823fe69b080e