Tweak how R packages are built.

Add bzip2 as a dependency to base R.

Switch from installing the R packages from tar files to installing from
the extracted directory. This is more in line with a standard install
and also allows installing from VCS.

Use the Bioconductor version for BiocGenerics and future Bioconductor
packages. Suffix the package with 'bioc-$version' to indicate which
Bioconductor release the package is a part of. This is actually more
important than the actual version attached to individual packages
although those are subject to change within the Bioconductor branch.

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

@@ -34,7 +34,7 @@ class RMagic(Package):
     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)
+    version('1.5-6', 'a68e5ced253b2196af842e1fc84fd029')
 
     extends('R')
 
@@ -42,4 +42,4 @@ class RMagic(Package):
 
     def install(self, spec, prefix):
         R('CMD', 'INSTALL', '--library=%s' %
-          self.module.r_lib_dir, '%s' % self.stage.archive_file)
+          self.module.r_lib_dir, '%s' % self.stage.source_path)