Adding cython v0.20.2 in third-party.

third_party/cython/src/Cython/Utility/Capsule.c

Index: third_party/cython/src/Cython/Utility/Capsule.c
diff --git a/third_party/cython/src/Cython/Utility/Capsule.c b/third_party/cython/src/Cython/Utility/Capsule.c
new file mode 100644
index 0000000000000000000000000000000000000000..b9d11ac242afb9eba3866773ca3050dc51a15fa1
--- /dev/null
+++ b/third_party/cython/src/Cython/Utility/Capsule.c
@@ -0,0 +1,20 @@
+//////////////// Capsule.proto ////////////////
+
+/* Todo: wrap the rest of the functionality in similar functions */
+static CYTHON_INLINE PyObject *__pyx_capsule_create(void *p, const char *sig);
+
+//////////////// Capsule ////////////////
+
+static CYTHON_INLINE PyObject *
+__pyx_capsule_create(void *p, CYTHON_UNUSED const char *sig)
+{
+    PyObject *cobj;
+
+#if PY_VERSION_HEX >= 0x02070000 && !(PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 0)
+    cobj = PyCapsule_New(p, sig, NULL);
+#else
+    cobj = PyCObject_FromVoidPtr(p, NULL);
+#endif
+
+    return cobj;
+}