Fix PR#15997, noquote columns in dataframe

git-svn-id: https://svn.r-project.org/R/trunk@66929 00db46b3-68df-0310-9c12-caf00c1e9a41
Copyright updates

git-svn-id: https://svn.r-project.org/R/trunk@66931 00db46b3-68df-0310-9c12-caf00c1e9a41