common/channel_type: wrapper for generated 'struct channel_type'.

We make it a first-class citizen internally, even though we won't use
it over the wire (at least, non-experimental builds).  This scheme
follows the latest draft, in which features are flagged compulsory.

We also add several helper functions.

Since uses the *even* bits (as per latest spec), not the *odd* bits,
we have some other fixups.

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

common/channel_type.h

@@ -0,0 +1,38 @@
+/* This represents a channel type: i.e. the sticky feature bits. */
+#ifndef LIGHTNING_COMMON_CHANNEL_TYPE_H
+#define LIGHTNING_COMMON_CHANNEL_TYPE_H
+#include "config.h"
+#include <common/features.h>
+#include <wire/channel_type_wiregen.h>
+
+/* Explicit channel types */
+struct channel_type *channel_type_none(const tal_t *ctx);
+struct channel_type *channel_type_static_remotekey(const tal_t *ctx);
+struct channel_type *channel_type_anchor_outputs(const tal_t *ctx);
+
+/* Duplicate a channel_type */
+struct channel_type *channel_type_dup(const tal_t *ctx,
+				      const struct channel_type *t);
+
+/* Derive channel type from feature negotiation */
+struct channel_type *default_channel_type(const tal_t *ctx,
+					  const struct feature_set *our_features,
+					  const u8 *their_features);
+
+/* Does this type include this feature? */
+bool channel_type_has(const struct channel_type *type, int feature);
+
+/* Are these two channel_types equivalent? */
+bool channel_type_eq(const struct channel_type *a,
+		     const struct channel_type *b);
+
+/* Is channel_type_eq() for any type in this array? */
+bool channel_type_eq_any(const struct channel_type *t,
+			 struct channel_type **arr);
+
+/* Return channel_type if this is acceptable, otherwise NULL */
+struct channel_type *channel_type_accept(const tal_t *ctx,
+					 const u8 *t,
+					 const struct feature_set *our_features,
+					 const u8 *their_features);
+#endif /* LIGHTNING_COMMON_CHANNEL_TYPE_H */