utils: tal_hexstr() helper.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

utils.h

@@ -0,0 +1,9 @@
+#ifndef LIGHTNING_UTILS_H
+#define LIGHTNING_UTILS_H
+#include "config.h"
+#include <ccan/tal/tal.h>
+
+/* Allocate and fill in a hex-encoded string of this data. */
+char *tal_hexstr(const tal_t *ctx, const void *data, size_t len);
+
+#endif /* LIGHTNING_UTILS_H */