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/ncurses/package.py

@@ -0,0 +1,33 @@
+from spack import *
+
+class Ncurses(Package):
+    """The ncurses (new curses) library is a free software emulation of curses
+       in System V Release 4.0, and more. It uses terminfo format, supports pads and
+       color and multiple highlights and forms characters and function-key mapping,
+       and has all the other SYSV-curses enhancements over BSD curses.
+    """
+
+    homepage = "http://invisible-island.net/ncurses/ncurses.html"
+
+    version('5.9', '8cb9c412e5f2d96bc6f459aa8c6282a1',
+            url='http://ftp.gnu.org/pub/gnu/ncurses/ncurses-5.9.tar.gz')
+    version('6.0', 'ee13d052e1ead260d7c28071f46eefb1',
+            url='http://ftp.gnu.org/pub/gnu/ncurses/ncurses-6.0.tar.gz')
+
+    def install(self, spec, prefix):
+        configure("--prefix=%s" % prefix,
+                  "--with-shared",
+                  "--enable-widec",
+                  "--disable-pc-files",
+                  "--without-ada")
+        make()
+        make("install")
+
+        configure("--prefix=%s" % prefix,
+                  "--with-shared",
+                  "--disable-widec",
+                  "--disable-pc-files",
+                  "--without-ada")
+        make()
+        make("install")
+