daemon: handle feechange requests.

I originally overloaded struct htlc for this, as they go through the
same states, but separating them turned out to be clearer.

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

daemon/feechange.h

@@ -0,0 +1,50 @@
+#ifndef LIGHTNING_DAEMON_FEECHANGE_H
+#define LIGHTNING_DAEMON_FEECHANGE_H
+#include "config.h"
+#include "feechange_state.h"
+#include "htlc.h"
+
+struct feechange {
+	/* What's the status */
+	enum feechange_state state; 
+	/* The rate. */
+	u64 fee_rate;
+};
+
+static inline enum htlc_side feechange_side(enum feechange_state state)
+{
+	if (state <= SENT_FEECHANGE_ACK_REVOCATION) {
+		return LOCAL;
+	} else {
+		assert(state < FEECHANGE_STATE_INVALID);
+		return REMOTE;
+	}
+}
+
+bool feechange_changestate(struct peer *peer,
+			   struct feechange *feechange,
+			   enum feechange_state oldstate,
+			   enum feechange_state newstate,
+			   bool db_commit);
+
+struct feechange *new_feechange(struct peer *peer,
+				u64 fee_rate,
+				enum feechange_state state);
+
+const char *feechange_state_name(enum feechange_state s);
+enum feechange_state feechange_state_from_name(const char *name);
+
+/* HTLC-add-style bitflags for each feechange state */
+int feechange_state_flags(enum feechange_state state);
+
+static inline bool feechange_has(const struct feechange *f, int flag)
+{
+	return feechange_state_flags(f->state) & flag;
+}
+
+static inline bool feechange_is_dead(const struct feechange *feechange)
+{
+	return feechange->state == SENT_FEECHANGE_ACK_REVOCATION
+		|| feechange->state == RCVD_FEECHANGE_ACK_REVOCATION;
+}
+#endif /* LIGHTNING_DAEMON_FEECHANGE_H */