use 64-bit counter for downloaded file sizes

git-svn-id: https://svn.r-project.org/R/trunk@66845 00db46b3-68df-0310-9c12-caf00c1e9a41
prefer KB, MB

git-svn-id: https://svn.r-project.org/R/trunk@66846 00db46b3-68df-0310-9c12-caf00c1e9a41
doc update

git-svn-id: https://svn.r-project.org/R/trunk@66847 00db46b3-68df-0310-9c12-caf00c1e9a41
doc update

git-svn-id: https://svn.r-project.org/R/trunk@66848 00db46b3-68df-0310-9c12-caf00c1e9a41
Add BOM.

git-svn-id: https://svn.r-project.org/R/trunk@66849 00db46b3-68df-0310-9c12-caf00c1e9a41
missing brace

git-svn-id: https://svn.r-project.org/R/trunk@66850 00db46b3-68df-0310-9c12-caf00c1e9a41