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/cppcheck/package.py

@@ -0,0 +1,15 @@
+from spack import *
+
+class Cppcheck(Package):
+    """A tool for static C/C++ code analysis."""
+    homepage = "http://cppcheck.sourceforge.net/"
+    url      = "http://downloads.sourceforge.net/project/cppcheck/cppcheck/1.68/cppcheck-1.68.tar.bz2"
+
+    version('1.68', 'c015195f5d61a542f350269030150708')
+
+    def install(self, spec, prefix):
+        # cppcheck does not have a configure script
+        make()
+        # manually install the final cppcheck binary
+        mkdirp(prefix.bin)
+        install('cppcheck', prefix.bin)