util/dump.c: Add hex pretty-print debug helper

util/dump.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <stddef.h>
+
+#include "hook/iobuf.h"
+
+#ifndef NDEBUG
+void dump(const void *ptr, size_t nbytes);
+void dump_iobuf(const struct iobuf *iobuf);
+void dump_const_iobuf(const struct const_iobuf *iobuf);
+#else
+#define dump(ptr, nbytes)
+#define dump_iobuf(iobuf)
+#define dump_const_iobuf(iobuf)
+#endif