Fix data range when copy a queue

[BHgin]

I encounterd an issue when I copied a queue_t that already has been popped from.
In an minimal example it looks like this:

constant QUEUE : queue_t := new_queue;
...
variable data_a : std_logic_vector(63 downto 0) := (others => '0');
variable data_b : std_logic_vector(63 downto 0) := (others => '1');
variable data : std_logic_vector(63 downto 0);
...
push(QUEUE, data_a);
push(QUEUE, data_b);

data := pop(QUEUE);
check_equal(data, data_a);

data := pop(copy(QUEUE)) -- is also data_a
check_equal(data, data_b); -- error, data_a instead of data_b was popped above!

The problem is that while copying the data of QUEUE the range 0 to length(queue) - 1 is used rather than the actual head and tail values get(queue.p_meta, head_idx) to get(queue.p_meta, tail_idx) - 1.

The copied queue still does not have the same head and tail as the origin but they have the same content and length.