add minimal winsock->BSD networking header shims

also add license header to existing shims

include/arpa/inet.h

@@ -0,0 +1,10 @@
+/*
+ * Public domain
+ * arpa/inet.h compatibility shim
+ */
+
+#ifndef _WIN32
+#include_next <arpa/inet.h>
+#else
+#include <win32netcompat.h>
+#endif