routing: Added IRC announcement glue

Added channel announcement serialization and parsing, as well as the
entrypoints for the IRC peer discovery. Announcements are signed by the
sending endpoint and signatures are verified before adding the channels
to the local view of the topology. We do not yet verify the existence of
the anchor transaction.

utils.h

@@ -1,9 +1,13 @@
 #ifndef LIGHTNING_UTILS_H
 #define LIGHTNING_UTILS_H
 #include "config.h"
+#include <ccan/short_types/short_types.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);
 
+/* Allocate and fill a buffer with the data of this hex string. */
+u8 *tal_hexdata(const tal_t *ctx, const void *str, size_t len);
+
 #endif /* LIGHTNING_UTILS_H */