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/py-coverage/package.py

@@ -0,0 +1,16 @@
+from spack import *
+
+class PyCoverage(Package):
+    """ Testing coverage checker for python """
+    # FIXME: add a proper url for your package's homepage here.
+    homepage = "http://nedbatchelder.com/code/coverage/"
+    url      = "https://pypi.python.org/packages/source/c/coverage/coverage-4.0a6.tar.gz"
+
+    version('4.0a6', '1bb4058062646148965bef0796b61efc')
+
+    depends_on('py-setuptools')
+
+    extends('python')
+
+    def install(self, spec, prefix):
+        python('setup.py', 'install', '--prefix=%s' % prefix)