miniupnpc: Update to version 2.2.3

Library code and public headers are now properly separated, we can fix include paths
to remove the redundant subfolder.

thirdparty/miniupnpc/src/minisoap.h

@@ -0,0 +1,17 @@
+/* $Id: minisoap.h,v 1.4 2010/04/12 20:39:41 nanard Exp $ */
+/* Project : miniupnp
+ * Author : Thomas Bernard
+ * Copyright (c) 2005-2018 Thomas Bernard
+ * This software is subject to the conditions detailed in the
+ * LICENCE file provided in this distribution. */
+#ifndef MINISOAP_H_INCLUDED
+#define MINISOAP_H_INCLUDED
+
+#include "miniupnpc_socketdef.h"
+
+/*int httpWrite(int, const char *, int, const char *);*/
+int soapPostSubmit(SOCKET, const char *, const char *, unsigned short,
+		   const char *, const char *, const char *);
+
+#endif
+