Fixed the warning from:
* checking S3 generic/method consistency ... OK
The issue was reusing an argument name incorrectly in plot.rwl. Seems like there is more to the S3Method than we are using.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/dplr@750 edb9625f-4e0d-4859-8d74-9fd3b1da38cb