Fixes :nodoc: on class aliases.  Fixes :stopdoc: creating references
	  to Object.  Fixes spacing when class comments are merged in ri.
	  Fixes `ri []` crash.  Fixes bug report URL when rdoc crashes.  Adds
	  :doc: and :nodoc: to allow hiding of implementation details in ruby.
	  Makes `rdoc` and `ri` gem-aware.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@32868 b2dd03c8-39d4-4d8f-98ff-823fe69b080e