r-rcpp: adds new versions, fixes failing download in Travis CI (#6464)
r-rcpp: adds new versions, fixes failing download in Travis CI (#6464)


tmerrick1/spack,krafczyk/spack,EmreAtes/spack,EmreAtes/spack,tmerrick1/spack,tmerrick1/spack,matthiasdiener/spack,matthiasdiener/spack,tmerrick1/spack,krafczyk/spack,LLNL/spack,matthiasdiener/spack,LLNL/spack,EmreAtes/spack,mfherbst/spack,matthiasdiener/spack,LLNL/spack,iulian787/spack,EmreAtes/spack,tmerrick1/spack,mfherbst/spack,iulian787/spack,EmreAtes/spack,LLNL/spack,krafczyk/spack,krafczyk/spack,LLNL/spack,krafczyk/spack,iulian787/spack,matthiasdiener/spack,mfherbst/spack,mfherbst/spack,iulian787/spack,iulian787/spack,mfherbst/spack