* lib/rdoc/generator/html.rb: Pull out ContextUser classes and related
	  methods for reuse.
	* lib/rdoc/generator.rb: Move ContextUser classes to
	  RDoc::Generator::Context for reuse.
	* lib/rdoc/rdoc.rb: Make RDoc::RDoc initialization a little easier.
	* lib/rdoc/options.rb: Make RDoc::Options easier to use without
	  parsing an ARGV.
	* lib/rdoc/markup/to_*.rb: Subclass RDoc::Markup::Formatter.
	* lib/rdoc/markup/formatter.rb: Add RDoc::Markup::Formatter to make
	  RDoc markup conversion easier.
	* lib/rdoc/markup/fragments.rb: Make RDoc::Markup::ListItem easier to
	  test.
	* lib/rdoc/markup/to_html_hyperlink.rb: Pulled out of the HTML
	  generator for easier reusability.
	* lib/rdoc/markup.rb: Fix bug with labeled lists containing bullet
	  lists.
	* lib/rdoc/generators/html/html.rb: Fix Constant display.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@15421 b2dd03c8-39d4-4d8f-98ff-823fe69b080e