Merge branch 'mplegendre-multi_pkgsrc_roots' into develop

- This moves var/spack/packages to var/spack/repos/builtin/packages.

- Packages that did not exist in the source branch, or were changed in
  develop, were moved into var/spack/repos/builtin/packages as part of
  the integration.

Conflicts:
	lib/spack/spack/test/unit_install.py
	var/spack/repos/builtin/packages/clang/package.py

var/spack/repos/builtin/packages/szip/package.py

@@ -0,0 +1,21 @@
+from spack import *
+
+class Szip(Package):
+    """Szip is an implementation of the extended-Rice lossless compression algorithm.
+    It provides lossless compression of scientific data, and is provided with HDF
+    software products."""
+
+    homepage = "https://www.hdfgroup.org/doc_resource/SZIP/"
+    url      = "http://www.hdfgroup.org/ftp/lib-external/szip/2.1/src/szip-2.1.tar.gz"
+
+    version('2.1', '902f831bcefb69c6b635374424acbead')
+
+    def install(self, spec, prefix):
+        configure('--prefix=%s' % prefix,
+                  '--enable-production',
+                  '--enable-shared',
+                  '--enable-static',
+                  '--enable-encoding')
+
+        make()
+        make("install")