Remove cryptoppwin submodule (#754)

third_party/cryptoppwin/include/cryptopp/nr.h

@@ -0,0 +1,11 @@
+// nr.h - originally written and placed in the public domain by Wei Dai
+
+/// \file nr.h
+/// \brief Classes for Nyberg-Rueppel signature scheme
+
+#ifndef CRYPTOPP_NR_H
+#define CRYPTOPP_NR_H
+
+#include "gfpcrypt.h"
+
+#endif