update

git-svn-id: https://svn.r-project.org/R/trunk@66871 00db46b3-68df-0310-9c12-caf00c1e9a41
add xref

git-svn-id: https://svn.r-project.org/R/trunk@66872 00db46b3-68df-0310-9c12-caf00c1e9a41
update

git-svn-id: https://svn.r-project.org/R/trunk@66874 00db46b3-68df-0310-9c12-caf00c1e9a41
clarify

git-svn-id: https://svn.r-project.org/R/trunk@66876 00db46b3-68df-0310-9c12-caf00c1e9a41
comment on clang options

git-svn-id: https://svn.r-project.org/R/trunk@66877 00db46b3-68df-0310-9c12-caf00c1e9a41
add comment on suppressLocalUnused
typos.


git-svn-id: https://svn.r-project.org/R/trunk@66879 00db46b3-68df-0310-9c12-caf00c1e9a41