more strict synchronization with <R-project-web>/contributors.html

git-svn-id: https://svn.r-project.org/R/trunk@66842 00db46b3-68df-0310-9c12-caf00c1e9a41
use an opaque type for download sizes

git-svn-id: https://svn.r-project.org/R/trunk@66843 00db46b3-68df-0310-9c12-caf00c1e9a41