New, cleaner package repository structure.

Package repositories now look like this:

    top-level-dir/
        repo.yaml
        packages/
            libelf/
                package.py
            mpich/
                package.py
            ...

This leaves room at the top level for additional metadata, source,
per-repo configs, indexes, etc., and it makes it easy to see that
something is a spack repo (just look for repo.yaml and packages).

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

@@ -0,0 +1,26 @@
+from spack import *
+
+class Openssl(Package):
+    """The OpenSSL Project is a collaborative effort to develop a
+       robust, commercial-grade, full-featured, and Open Source
+       toolkit implementing the Secure Sockets Layer (SSL v2/v3) and
+       Transport Layer Security (TLS v1) protocols as well as a
+       full-strength general purpose cryptography library."""
+    homepage = "http://www.openssl.org"
+    url      = "http://www.openssl.org/source/openssl-1.0.1h.tar.gz"
+
+    version('1.0.1h', '8d6d684a9430d5cc98a62a5d8fbda8cf')
+
+    depends_on("zlib")
+    parallel = False
+
+    def install(self, spec, prefix):
+        config = Executable("./config")
+        config("--prefix=%s" % prefix,
+               "--openssldir=%s/etc/openssl" % prefix,
+               "zlib",
+               "no-krb5",
+               "shared")
+
+        make()
+        make("install")