* lib/rexml/encodings/: remove. * lib/rexml/document.rb, lib/rexml/formatters/default.rb, lib/rexml/output.rb, lib/rexml/parseexception.rb, lib/rexml/parsers/baseparser.rb, lib/rexml/source.rb, lib/rexml/xmldecl.rb: use Ruby's native Encoding object. * test/rexml/, test/rss/: follow the above encoding chagnes. * NEWS: add REXML's incompatible change about encoding. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29646 b2dd03c8-39d4-4d8f-98ff-823fe69b080e