Re-add list_url for all R packages (#6110)

* r-igraph: find old packages in the archive

Fixes #6104.

* r-irlba: find old packages in the archive

Fixes #6101.

* r-lazyeval: find old packages in the archive

Fixes #6102.

* packages: set list_url for all packages hosted on CRAN

* packages: consistently use the CRAN archive URLs

var/spack/repos/builtin/packages/r-rstan/package.py

@@ -38,6 +38,7 @@ class RRstan(RPackage):
 
     homepage = "http://mc-stan.org/"
     url      = "https://cran.r-project.org/src/contrib/rstan_2.10.1.tar.gz"
+    list_url = "https://cran.r-project.org/src/contrib/Archive/rstan"
 
     version('2.10.1', 'f5d212f6f8551bdb91fe713d05d4052a')