[Fluxus] Errors with start-audio and jack: memlock limits and real-time permissions

[Javier Candeira]

Hi again,

I was following the tutorial, and I got an error when first trying to read 
audio into Fluxus and using it for animation:

```
jcz at darthvader:~$ fluxus temp.scm
Welcome to fluxus.
Type (help) for info.
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
Cannot use real-time scheduling (RR/5)(1: Operation not permitted)
JackClient::AcquireSelfRealTime error
```

The script I was running at the time:

```
(clear)
(start-audio "system:capture_1" 1024 44100)
(define (armonics)
     (colour (vector (gh 0) (gh 1) (gh 2)))
     (draw-cube))

(every-frame (armonics))
```

And the audio configuration seems right, I was just playing music videos on 
a browser and using jack to connect main PC output to input:

```
21:26:56.676 JACK connection graph change.
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
Tue Oct  8 21:26:56 2019: New client 'qjackctl' with PID 3552
21:27:09.139 Transport start.
21:27:32.764 JACK connection change.
Tue Oct  8 21:27:32 2019: Connecting 'system:capture_1' to 'system:playback_1'
21:27:36.365 JACK connection change.
Tue Oct  8 21:27:36 2019: Connecting 'system:capture_2' to 'system:playback_2'
21:28:29.283 JACK connection graph change.
21:28:29.339 JACK connection change.
Tue Oct  8 21:28:29 2019: New client 'Fluxus' with PID 5324
Tue Oct  8 21:28:29 2019: Connecting 'system:capture_1' to 'Fluxus:In0'
```

I'm running Jack through something called QjackCtl, which was what Ubuntu 
shows when you put "jack" into the Gnome Shell search box.

Cheers,
Javier