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/tau/package.py

@@ -0,0 +1,36 @@
+from spack import *
+
+import os
+from llnl.util.filesystem import join_path
+
+class Tau(Package):
+    """A portable profiling and tracing toolkit for performance
+       analysis of parallel programs written in Fortran, C, C++, UPC,
+       Java, Python."""
+    homepage = "http://www.cs.uoregon.edu/research/tau"
+    url      = "http://www.cs.uoregon.edu/research/paracomp/tau/tauprofile/dist/tau-2.23.1.tar.gz"
+
+    version('2.23.1', '6593b47ae1e7a838e632652f0426fe72')
+
+    def install(self, spec, prefix):
+        # TAU isn't happy with directories that have '@' in the path.  Sigh.
+        change_sed_delimiter('@', ';', 'configure')
+        change_sed_delimiter('@', ';', 'utils/FixMakefile')
+        change_sed_delimiter('@', ';', 'utils/FixMakefile.sed.default')
+
+        # After that, it's relatively standard.
+        configure("-prefix=%s" % prefix)
+        make("install")
+
+        # Link arch-specific directories into prefix since there is
+        # only one arch per prefix the way spack installs.
+        self.link_tau_arch_dirs()
+
+
+    def link_tau_arch_dirs(self):
+        for subdir in os.listdir(self.prefix):
+            for d in ('bin', 'lib'):
+                src  = join_path(self.prefix, subdir, d)
+                dest = join_path(self.prefix, d)
+                if os.path.isdir(src) and not os.path.exists(dest):
+                    os.symlink(join_path(subdir, d), dest)