tweak wording

git-svn-id: https://svn.r-project.org/R/trunk@63275 00db46b3-68df-0310-9c12-caf00c1e9a41
stop continual re-build

git-svn-id: https://svn.r-project.org/R/trunk@63276 00db46b3-68df-0310-9c12-caf00c1e9a41
grammar, clarifications

git-svn-id: https://svn.r-project.org/R/trunk@63278 00db46b3-68df-0310-9c12-caf00c1e9a41