Add Tcl/Tk packages.

var/spack/packages/tcl/package.py

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+from spack import *
+
+class Tcl(Package):
+    """Tcl (Tool Command Language) is a very powerful but easy to
+       learn dynamic programming language, suitable for a very wide
+       range of uses, including web and desktop applications,
+       networking, administration, testing and many more. Open source
+       and business-friendly, Tcl is a mature yet evolving language
+       that is truly cross platform, easily deployed and highly
+       extensible."""
+    homepage = "http://www.tcl.tk"
+
+    version('8.6.3', 'db382feca91754b7f93da16dc4cdad1f',
+            url="http://prdownloads.sourceforge.net/tcl/tcl8.6.3-src.tar.gz")
+
+    depends_on('zlib')
+
+    def install(self, spec, prefix):
+        with working_dir('unix'):
+            configure("--prefix=%s" % prefix)
+            make()
+            make("install")

var/spack/packages/tk/package.py

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+from spack import *
+
+class Tk(Package):
+    """Tk is a graphical user interface toolkit that takes developing
+       desktop applications to a higher level than conventional
+       approaches. Tk is the standard GUI not only for Tcl, but for
+       many other dynamic languages, and can produce rich, native
+       applications that run unchanged across Windows, Mac OS X, Linux
+       and more."""
+    homepage = "http://www.tcl.tk"
+    url      = "http://prdownloads.sourceforge.net/tcl/tk8.6.3-src.tar.gz"
+
+    version('src', '85ca4dbf4dcc19777fd456f6ee5d0221')
+
+    depends_on("tcl")
+
+    def install(self, spec, prefix):
+        with working_dir('unix'):
+            configure("--prefix=%s" % prefix,
+                      "--with-tcl=%s" % spec['tcl'].prefix.lib)
+            make()
+            make("install")