document r63514

git-svn-id: https://svn.r-project.org/R/trunk@63515 00db46b3-68df-0310-9c12-caf00c1e9a41
add some regression tests

git-svn-id: https://svn.r-project.org/R/trunk@63517 00db46b3-68df-0310-9c12-caf00c1e9a41