Removing Serendipity's NL2BR Plugin

I've been getting tired of fighting Serendipity's NL2BR Plugin, which automatically inserts line breaks in blog entries. It got difficult to format things like source code. This blog entry contains a useful piece of SQL to update your previous entries. Then it's just a matter of disabling the NL2BR Plugin. After going through those steps, my blog appears to look the same, and now I don't have to worry about the NL2BR problems anymore.