merge revision(s) 40372: [Backport #8167]

	* lib/net/imap.rb (body_type_msg): should accept
	  message/delivery-status with extra data.
	  [ruby-core:53741] [Bug #8167]

	* test/net/imap/test_imap_response_parser.rb: related test.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@46733 b2dd03c8-39d4-4d8f-98ff-823fe69b080e