All of these lines are trying to set HTTP headers. I cannot be sure unless you show the error in full, but I suspect this is because something has already been output to the browser by the time these lines are reached, so the HTTP headers can no longer be set.
I don't think this is a problem in the release itself, so perhaps you modified a file, maybe accidentally. It can be as simple as a blank line outside of <?php ?> tags, creating by a mistaken press of the return key on your keyboard.
If you view the error in full, it should tell you exactly where this output happened - in which file, and in which line, so you can check there.
