Backport 16029 fix to R-patched.

git-svn-id: https://svn.r-project.org/R/trunk@66976 00db46b3-68df-0310-9c12-caf00c1e9a41
Remove "experimental".

git-svn-id: https://svn.r-project.org/R/trunk@66977 00db46b3-68df-0310-9c12-caf00c1e9a41