fixes to Rtnmin


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/optimizer@871 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
cosmetic fixes


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/optimizer@872 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
add test fn


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/optimizer@873 edb9625f-4e0d-4859-8d74-9fd3b1da38cb