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/libpciaccess/package.py

@@ -0,0 +1,23 @@
+from spack import *
+import os.path
+
+class Libpciaccess(Package):
+    """Generic PCI access library."""
+
+    homepage = "http://cgit.freedesktop.org/xorg/lib/libpciaccess/"
+    url      = "http://xorg.freedesktop.org/archive/individual/lib/libpciaccess-0.13.4.tar.bz2"
+
+    version('0.13.4', 'ace78aec799b1cf6dfaea55d3879ed9f')
+
+    depends_on('libtool')
+
+    def install(self, spec, prefix):
+        # libpciaccess does not support OS X
+        if spec.satisfies('=darwin-x86_64'):
+            # create a dummy directory
+            mkdir(prefix.lib)
+            return
+
+        configure("--prefix=%s" % prefix)
+        make()
+        make("install")