factor out and quiet update.packages()
a (hopefully) final attempt to install packages that were built under R 2.x
update branch Thu Oct  2 02:29:02 CDT 2014
update branch knitr Thu Oct  2 13:02:26 CDT 2014
update branch knitr Thu Oct  2 14:49:45 CDT 2014
update branch knitr Thu Oct  2 19:41:50 CDT 2014