catch up with R-patched

git-svn-id: https://svn.r-project.org/R/trunk@63500 00db46b3-68df-0310-9c12-caf00c1e9a41
catch up with R-patched

git-svn-id: https://svn.r-project.org/R/trunk@63501 00db46b3-68df-0310-9c12-caf00c1e9a41
check for mandatory fields early

git-svn-id: https://svn.r-project.org/R/trunk@63504 00db46b3-68df-0310-9c12-caf00c1e9a41