Make R extensable and add a couple of packages for verification.

Added R as a build system so that the create template will have the
correct configure line.
Added a regex for version parsing as the R URLs are a little odd.

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

@@ -0,0 +1,15 @@
+from spack import *
+
+class RMagic(Package):
+    """A collection of efficient, vectorized algorithms for the creation and investigation of magic squares and hypercubes, including a variety of functions for the manipulation and analysis of arbitrarily dimensioned arrays."""
+    homepage = "https://cran.r-project.org/"
+    url      = "https://cran.r-project.org/src/contrib/magic_1.5-6.tar.gz"
+
+    version('1.5-6', 'a68e5ced253b2196af842e1fc84fd029', expand=False)
+
+    extends('R')
+
+    depends_on('r-abind')
+
+    def install(self, spec, prefix):
+        R('CMD', 'INSTALL', '--library=%s' % self.module.r_lib_dir, '%s' % self.stage.archive_file)