main: pack struct fhs

```
struct fhs {
        struct le                  le;                   /*     0    32 */
        _Bool                      active;               /*    32     1 */

        /* XXX 3 bytes hole, try to pack */

        re_sock_t                  fd;                   /*    36     4 */
        int                        flags;                /*    40     4 */

        /* XXX 4 bytes hole, try to pack */

        fd_h *                     fh;                   /*    48     8 */
        void *                     arg;                  /*    56     8 */

        /* size: 64, cachelines: 1, members: 6 */
        /* sum members: 57, holes: 2, sum holes: 7 */
};
```

src/main/main.c

@@ -69,11 +69,11 @@ enum {
 /** File descriptor handler struct */
 struct fhs {
 	struct le le; 	     /**< Hash/Delete entry                 */
-	bool active;         /**< In-use                            */
 	re_sock_t fd;        /**< File Descriptor                   */
 	int flags;           /**< Polling flags (Read, Write, etc.) */
 	fd_h* fh;            /**< Event handler                     */
 	void* arg;           /**< Handler argument                  */
+	bool active;         /**< In-use                            */
 };
 
 /** Polling loop data */