configure-test for realpath

git-svn-id: https://svn.r-project.org/R/trunk@63253 00db46b3-68df-0310-9c12-caf00c1e9a41
put LICENSE in tarball

git-svn-id: https://svn.r-project.org/R/trunk@63254 00db46b3-68df-0310-9c12-caf00c1e9a41