win.version() reports Windows 8/Server 2012.

git-svn-id: https://svn.r-project.org/R/trunk@61668 00db46b3-68df-0310-9c12-caf00c1e9a41
Fix myR target in Windows installer.

git-svn-id: https://svn.r-project.org/R/trunk@61670 00db46b3-68df-0310-9c12-caf00c1e9a41