jQuery to override SharePoint OOTB Upload.aspx default for "Add as a new version to existing files" checkbox

A common query from SharePoint users with versioning enabled on document libraries is to default the "Add as a new version to existing files" checkbox on the OOTB upload.aspx page to unchecked. If you google how to uncheck it by default you'll get lots of entries showing you how to simply edit the Upload.aspx file in the \TEMPLATE\LAYOUTS\ folder in the 12/14 hive. This works fine of course if you don't care about tomorrow and having a supported/upgradeable SharePoint installation.