section -> section*

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/zoo@984 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
improved implementation of 'drop'

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/zoo@985 edb9625f-4e0d-4859-8d74-9fd3b1da38cb