ir: add BT_CTF_MOVE()

ir: add BT_CTF_MOVE()

Adds semantics to ownership transfers of CTF IR objects.

This is something that is done often enough to justify the
existence of this macro:

    struct bt_ctf_field_type *type;
    struct bt_ctf_field_type *ret_type;

    /* ... */

    /* move ownership */
    ret_type = type;
    type = NULL;

    /* ... */

    /* put both (safe since type was set to NULL) */
    bt_ctf_put(ret_type);
    bt_ctf_put(type);

With BT_CTF_MOVE():

    struct bt_ctf_field_type *type;
    struct bt_ctf_field_type *ret_type;

    /* ... */

    /* move ownership */
    BT_CTF_MOVE(ret_type, type);

    /* ... */

    /* put both (safe since ownership was moved) */
    bt_ctf_put(ret_type);
    bt_ctf_put(type);

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>