To quote a former colleague "You're doing it wrong".
AS 7 is a completely new architecture compared to the former AS releases. Instead of embedding datasource definitions inside your EAR deployment they should be part of the deployment plan for the application.
As Jason states you can use the @DataSourceDefinition, however you won't get the benefit of being in management controlled environment - and hence you won't get the benefits of the JCA container and all features in the container itself and the JDBC resource adapter, such as prepared statement cache and so on. Look the datasource schema over, and see what you are going to manage yourself plus of course all the management features of the AS itself.
Why not try to use Alexey's CLI tool (jboss-admin.sh) to create the deployment plan that you are looking for - if there are any missing features we are always looking for feedback.
Having said that, this is open source - you are more than welcome to contribute to the project.