radio.config queue parameter

The queue parameter in radio.config() does not seem to have an affect. Even when not set (and so the queue default is set to 3) the micro:bit seems to be able to store at least 10 messages in the queue.

# To recreate:
flash the contents of this script onto a micro:bit:
```
from microbit import *
import radio

# turn on the radio
radio.on()
cpt = 0

while True:
if button_a.was_pressed():
radio.send(str(cpt))
cpt = cpt + 1

sleep(100)
```

Then, by pressing A 5 times, send 5 different messages to another micro:bit set up to receive them - you will need to put into the terminal:

```
>>>from micro:bit import *
>>>import radio
>>>radio.config(queue=1)
>>>radio.receive()
0
>>>radio.receive()
1
>>>radio.receive()
2
etc
```

you should get at least 5 different messages, which shows more than 1 message is being stored on the queue.