more cleaning up

git-svn-id: https://svn.r-project.org/R/trunk@67038 00db46b3-68df-0310-9c12-caf00c1e9a41
documentation tweaks

git-svn-id: https://svn.r-project.org/R/trunk@67039 00db46b3-68df-0310-9c12-caf00c1e9a41
add link

git-svn-id: https://svn.r-project.org/R/trunk@67041 00db46b3-68df-0310-9c12-caf00c1e9a41
clarifications

git-svn-id: https://svn.r-project.org/R/trunk@67042 00db46b3-68df-0310-9c12-caf00c1e9a41
switch defaults to --with-system-{zlib,bzlib,pcre}

git-svn-id: https://svn.r-project.org/R/trunk@67044 00db46b3-68df-0310-9c12-caf00c1e9a41
document deprecation

git-svn-id: https://svn.r-project.org/R/trunk@67045 00db46b3-68df-0310-9c12-caf00c1e9a41
tweaks to extSoftVersion()

git-svn-id: https://svn.r-project.org/R/trunk@67046 00db46b3-68df-0310-9c12-caf00c1e9a41