un.rb: nodoc setup

* lib/un.rb (setup): nodoc for internal use method.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41798 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
un.rb: refine regexp

* lib/un.rb (help): refine regexp to extract method name.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41799 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
un.rb: help message

* lib/un.rb (setup): show help message by help method.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41800 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
un.rb: help order

* lib/un.rb (UN#help): show help messages in the given order.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41801 b2dd03c8-39d4-4d8f-98ff-823fe69b080e