[db] added new DB_CAP_PREPARED_STMT capability

to identify the db backends able to provide prepared statements.
DB_MYSQL is for now the only condidate

db/db_cap.h

@@ -48,6 +48,7 @@ typedef enum db_cap {
 	DB_CAP_LAST_INSERTED_ID = 1 << 8,  /**< driver can return the ID of the last insert operation   */
 	DB_CAP_INSERT_UPDATE    = 1 << 9,  /**< driver can insert data into database and update on duplicate */
 	DB_CAP_MULTIPLE_INSERT  = 1 << 10,  /**< driver can insert multiple rows at once */
+	DB_CAP_PREPARED_STMT    = 1 << 11,  /**< driver supports prep statements */
 } db_cap_t;
 
 

modules/db_mysql/db_mysql.c

@@ -179,7 +179,7 @@ int db_mysql_bind_api(const str* mod, db_func_t *dbb)
 	dbb->async_free_result = db_mysql_async_free_result;
 	dbb->async_timeout     = db_mysql_async_timeout;
 
-	dbb->cap |= DB_CAP_MULTIPLE_INSERT;
+	dbb->cap |= DB_CAP_MULTIPLE_INSERT|DB_CAP_PREPARED_STMT;
 	return 0;
 }