[cdatapack] adds an initial cpython file for the cdatapack implementation

Summary: Just a simple module declaration with no logic yet.

Test Plan:
```
[andromeda]:~/work/mercurial/facebook-hg-rpms/remotefilelog:2445a3a> make local

<output snipped>

[andromeda]:~/work/mercurial/facebook-hg-rpms/remotefilelog:2445a3a> python
Python 2.7.11 (default, Mar  1 2016, 18:40:10)
[GCC 4.2.1 Compatible Apple LLVM 7.0.2 (clang-700.1.81)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import cdatapack
>>>
```

Reviewers: #fastmanifest, durham

Reviewed By: durham

Subscribers: mitrandir

Differential Revision: https://phabricator.intern.facebook.com/D3654786

Signature: t1:3654786:1470175354:c7e8847dcc74c83483d21888ad30cd9242fb461c

remotefilelog/cdatapack/py-cdatapack.c

@@ -0,0 +1,23 @@
+// py-cdatapack.cpp - C implementation of a datapack
+//
+// Copyright 2016 Facebook, Inc.
+//
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2 or any later version.
+//
+// no-check-code
+
+#include <Python.h>
+
+static PyMethodDef mod_methods[] = {
+  {NULL, NULL}
+};
+
+static char mod_description[] =
+    "Module containing a native datapack implementation";
+
+PyMODINIT_FUNC initcdatapack(void) {
+  PyObject *mod;
+
+  mod = Py_InitModule3("cdatapack", mod_methods, mod_description);
+}

setup.py

@@ -14,5 +14,15 @@ setup(
     license='GPLv2+',
     packages=['remotefilelog'],
     install_requires=['lz4'],
-    ext_modules = []
+    ext_modules = [
+        Extension('cdatapack',
+                  sources=[
+                      'remotefilelog/cdatapack/py-cdatapack.c',
+                  ],
+                  extra_compile_args=[
+                      "-std=c99",
+                      "-Wall",
+                      "-Werror", "-Werror=strict-prototypes"],
+        )
+    ],
 )