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/extrae/package.py

@@ -0,0 +1,46 @@
+from spack import *
+
+# typical working line with extrae 3.0.1
+# ./configure --prefix=/usr/local --with-mpi=/usr/lib64/mpi/gcc/openmpi --with-unwind=/usr/local --with-papi=/usr --with-dwarf=/usr --with-elf=/usr --with-dyninst=/usr --with-binutils=/usr --with-xml-prefix=/usr --enable-openmp --enable-nanos --enable-pthread --disable-parallel-merge LDFLAGS=-pthread
+
+class Extrae(Package):
+    """Extrae is the package devoted to generate tracefiles which can
+       be analyzed later by Paraver. Extrae is a tool that uses
+       different interposition mechanisms to inject probes into the
+       target application so as to gather information regarding the
+       application performance. The Extrae instrumentation package can
+       instrument the MPI programin model, and the following parallel
+       programming models either alone or in conjunction with MPI :
+       OpenMP, CUDA, OpenCL, pthread, OmpSs"""
+    homepage = "http://www.bsc.es/computer-sciences/extrae"
+    url      = "http://www.bsc.es/ssl/apps/performanceTools/files/extrae-3.0.1.tar.bz2"
+    version('3.0.1', 'a6a8ca96cd877723cd8cc5df6bdb922b')
+
+    depends_on("mpi")
+    depends_on("dyninst")
+    depends_on("libunwind")
+    depends_on("boost")
+    depends_on("libdwarf")
+    depends_on("papi")
+
+    def install(self, spec, prefix):
+        if 'openmpi' in spec:
+            mpi = spec['openmpi']
+        elif 'mpich' in spec:
+            mpi = spec['mpich']
+        elif 'mvapich2' in spec:
+            mpi = spec['mvapich2']
+
+        configure("--prefix=%s"				% prefix,
+	            "--with-mpi=%s"				% mpi.prefix,
+	            "--with-unwind=%s"			% spec['libunwind'].prefix,
+	            "--with-dyninst=%s"			% spec['dyninst'].prefix,
+	            "--with-boost=%s"			% spec['boost'].prefix,
+	            "--with-dwarf=%s"			% spec['libdwarf'].prefix,
+	            "--with-papi=%s"			% spec['papi'].prefix,
+	            "--with-dyninst-headers=%s"	% spec['dyninst'].prefix.include,
+	            "--with-dyninst-libs=%s"	% spec['dyninst'].prefix.lib)
+
+        make()
+        make("install", parallel=False)
+