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/stat/configure_mpicxx.patch

@@ -0,0 +1,19 @@
+commit 07ab6e565f939c54fff6580fc8463ea61662871a
+Author: Gregory L. Lee <lee218@llnl.gov>
+Date:   Tue May 20 14:53:35 2014 -0700
+
+    re-boostrap to update configure
+
+diff --git a/configure b/configure
+index 6c4af7d..30901ea 100755
+--- a/configure
++++ b/configure
+@@ -15529,7 +15529,7 @@ fi
+ done
+ test -n "$MPICC" || MPICC="$CC"
+ 
+-  for ac_prog in mpig++ mpiicpc mpxlC mpixlC
++  for ac_prog in mpig++ mpiCC mpicxx mpiicpc mpxlC mpixlC
+ do
+   # Extract the first word of "$ac_prog", so it can be a program name with args.
+ set dummy $ac_prog; ac_word=$2

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

@@ -0,0 +1,40 @@
+from spack import *
+
+class Stat(Package):
+    """Library to create, manipulate, and export graphs Graphlib."""
+    homepage = "http://paradyn.org/STAT/STAT.html"
+    url      = "https://github.com/lee218llnl/stat/archive/v2.0.0.tar.gz"
+
+    version('2.2.0', '26bd69dd57a15afdd5d0ebdb0b7fb6fc')
+    version('2.1.0', 'ece26beaf057aa9134d62adcdda1ba91')
+    version('2.0.0', 'c7494210b0ba26b577171b92838e1a9b')
+
+    variant('dysect', default=False, description="enable DySectAPI")
+
+    depends_on('libelf')
+    depends_on('libdwarf')
+    depends_on('dyninst')
+    depends_on('graphlib')
+    depends_on('graphviz')
+    depends_on('launchmon')
+    depends_on('mrnet')
+
+    patch('configure_mpicxx.patch', when='@2.1.0')
+
+    def install(self, spec, prefix):
+        configure_args = [
+            "--enable-gui",
+            "--prefix=%s" % prefix,
+            "--disable-examples", # Examples require MPI: avoid this dependency.
+            "--with-launchmon=%s"   % spec['launchmon'].prefix,
+            "--with-mrnet=%s"       % spec['mrnet'].prefix,
+            "--with-graphlib=%s"    % spec['graphlib'].prefix,
+            "--with-stackwalker=%s" % spec['dyninst'].prefix,
+            "--with-libdwarf=%s"    % spec['libdwarf'].prefix
+            ]
+        if '+dysect' in spec:
+            configure_args.append('--enable-dysectapi')
+        configure(*configure_args)
+
+        make(parallel=False)
+        make("install")