wally: override wally to use tal-context

See attached. This lets us do fancy things with tal_steal

common/daemon.c

@@ -18,6 +18,8 @@
 #include <unistd.h>
 #include <wally_core.h>
 
+static const tal_t *wally_tal_ctx;
+
 #if BACKTRACE_SUPPORTED
 static void (*bt_print)(const char *fmt, ...) PRINTF_FMT(1,2);
 static void (*bt_exit)(void);
@@ -119,6 +121,21 @@ static void add_steal_notifiers(const tal_t *root)
 }
 #endif
 
+static void *wally_tal(size_t size)
+{
+	return tal_arr_label(wally_tal_ctx, u8, size, "wally_notleak");
+}
+
+static void wally_free(void *ptr)
+{
+	tal_free(ptr);
+}
+
+static struct wally_operations wally_tal_ops = {
+	.malloc_fn = wally_tal,
+	.free_fn = wally_free,
+};
+
 void daemon_setup(const char *argv0,
 		  void (*backtrace_print)(const char *fmt, ...),
 		  void (*backtrace_exit)(void))
@@ -153,7 +170,11 @@ void daemon_setup(const char *argv0,
 
 	/* We handle write returning errors! */
 	signal(SIGPIPE, SIG_IGN);
+
+	/* We set up Wally, the bitcoin wallet lib */
+	wally_tal_ctx = tal_label(NULL, char, "wally_ctx_notleak");
 	wally_init(0);
+	wally_set_operations(&wally_tal_ops);
 	secp256k1_ctx = wally_get_secp_context();
 
 	setup_tmpctx();
@@ -164,6 +185,7 @@ void daemon_shutdown(void)
 {
 	tal_free(tmpctx);
 	wally_cleanup(0);
+	wally_free(wally_tal_ctx);
 }
 
 void daemon_maybe_debug(char *argv[])