* added methods XMLRPC::XMLParser.each_installed_parser and
XMLRPC::XMLWriter.each_installed_writer to simply original test cases
* use Object#allocate instead of defining an empty #initialize
* module XMLRPC::Marshallable is now only used for tagging
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@7274 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
