dplR 1.5.9

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/dplr@733 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Preparing for dplR 1.6.0, assuming the current version number scheme

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/dplr@734 edb9625f-4e0d-4859-8d74-9fd3b1da38cb