merge revision(s) r47973: [Backport #10392]

	* parse.y (parser_here_document): do not append already appended
	  and disposed code fragment.  [ruby-dev:48647] [Bug #10392]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@48003 b2dd03c8-39d4-4d8f-98ff-823fe69b080e