Fixed assertion that were broken with recent delayed header response.

Changed semantic of put_header_lines and add_header_lines,
Now the arguments are iterable of string (i.e the header line)

The previous features were not used, and were not well named.
So we removed them, and reused the names for adpated implementation.

library/server/ewsgi/specification/response/wgi_response.e

@@ -11,17 +11,17 @@ feature {WGI_CONNECTOR, WGI_SERVICE} -- Commit
 	push
 			-- Commit and push response
 		do
-			commit
 			if attached post_commit_action as act then
 				act.call (Void)
 			end
+			commit
 		end
 
 	commit
 			-- Commit the current response
 		deferred
 		ensure
-			status_is_set: status_is_set
+			status_committed: status_committed
 			header_committed: header_committed
 			message_committed: message_committed
 		end