add check that Authors@R was used

git-svn-id: https://svn.r-project.org/R/trunk@63955 00db46b3-68df-0310-9c12-caf00c1e9a41
ignore whitespace in comparison

git-svn-id: https://svn.r-project.org/R/trunk@63956 00db46b3-68df-0310-9c12-caf00c1e9a41