wallet: Move the struct db definition to db_common.h

All drivers will have to reach into it, so put it in a place that is reachable
from the drivers, along with all other definitions.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

wallet/db.c

@@ -19,21 +19,6 @@ struct migration {
 	void (*func)(struct lightningd *ld, struct db *db);
 };
 
-struct db {
-	char *filename;
-	const char *in_transaction;
-	sqlite3 *sql;
-
-	/* DB-specific context */
-	void *conn;
-
-	/* The configuration, including translated queries for the current
-	 * instance. */
-	const struct db_config *config;
-
-	const char **changes;
-};
-
 void migrate_pr2342_feerate_per_channel(struct lightningd *ld, struct db *db);
 
 /* Do not reorder or remove elements from this array, it is used to

wallet/db_common.h

@@ -3,11 +3,29 @@
 #include "config.h"
 #include <ccan/autodata/autodata.h>
 #include <ccan/short_types/short_types.h>
+#include <sqlite3.h>
+
 /* For testing, we want to catch fatal messages. */
 #ifndef db_fatal
 #define db_fatal fatal
 #endif
 
+struct db {
+	char *filename;
+	const char *in_transaction;
+	sqlite3 *sql;
+
+	/* DB-specific context */
+	void *conn;
+
+	/* The configuration, including translated queries for the current
+	 * instance. */
+	const struct db_config *config;
+
+	const char **changes;
+
+	char *error;
+};
 
 struct db_query {
 	const char *name;