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/opari2/package.py

@@ -0,0 +1,65 @@
+# FIXME: Add copyright statement here 
+
+from spack import *
+from contextlib import closing
+
+class Opari2(Package):
+    """OPARI2 is a source-to-source instrumentation tool for OpenMP and 
+       hybrid codes. It surrounds OpenMP directives and runtime library 
+       calls with calls to the POMP2 measurement interface.
+       OPARI2 will provide you with a new initialization method that allows 
+       for multi-directory and parallel builds as well as the usage of 
+       pre-instrumented libraries. Furthermore, an efficient way of 
+       tracking parent-child relationships was added. Additionally, we 
+       extended OPARI2 to support instrumentation of OpenMP 3.0 
+       tied tasks. """
+
+    homepage = "http://www.vi-hps.org/projects/score-p"
+    url      = "http://www.vi-hps.org/upload/packages/opari2/opari2-1.1.2.tar.gz"
+
+    version('1.1.2', '9a262c7ca05ff0ab5f7775ae96f3539e')
+
+    backend_user_provided = """\
+CC=cc
+CXX=c++
+F77=f77
+FC=f90
+CFLAGS=-fPIC
+CXXFLAGS=-fPIC
+"""
+    frontend_user_provided = """\
+CC_FOR_BUILD=cc
+CXX_FOR_BUILD=c++
+F77_FOR_BUILD=f70
+FC_FOR_BUILD=f90
+CFLAGS_FOR_BUILD=-fPIC
+CXXFLAGS_FOR_BUILD=-fPIC
+"""
+    mpi_user_provided = """\
+MPICC=mpicc
+MPICXX=mpicxx
+MPIF77=mpif77
+MPIFC=mpif90
+MPI_CFLAGS=-fPIC
+MPI_CXXFLAGS=-fPIC
+"""
+
+    def install(self, spec, prefix):
+        # Use a custom compiler configuration, otherwise the score-p
+        # build system messes with spack's compiler settings.
+        # Create these three files in the build directory
+        with closing(open("platform-backend-user-provided", "w")) as backend_file:
+            backend_file.write(self.backend_user_provided)
+        with closing(open("platform-frontend-user-provided", "w")) as frontend_file:
+            frontend_file.write(self.frontend_user_provided)
+        with closing(open("platform-mpi-user-provided", "w")) as mpi_file:
+            mpi_file.write(self.mpi_user_provided)            
+
+        # FIXME: Modify the configure line to suit your build system here.
+        configure("--prefix=%s" % prefix,
+                  "--with-custom-compilers",
+                  "--enable-shared")
+
+        # FIXME: Add logic to build and install here
+        make()
+        make("install")