Fixes in plugin.xml template, added DTD definition into it. Version element have automatical generation token for since-build IDEA build number. For example, if you deploy your plugin with since-build="@idea.build.number@" then ANT automaticaly get build number from IDEA home, and your plugin have correctly build version since it working.
If you already have this ANT script installation, just perform 'ant update' in directory where script installed.
If you have not installation you can get latest one from
Installation new ant script over existing project will backup your previous scripts, and you can quickly fix new build.properties for new build.xml.