[Simh] Photorealistic panel for PDP-11/20

[Jörg Hoppe]

The header line says it all: another panel for BlinkenBone is there, the 
classic PDP-11/20.
In function and style it fills the gap between the PDP-8 and the later 
PDP-11's.

The GitHub distribution starts the 1970 Paper-tape BASIC, download here:
https://github.com/j-hoppe/BlinkenBone/releases

For info see
http://retrocmp.com/projects/blinkenbone/simulated-panels/253-blinkenbone-simulated-pdp-11-20-panel
and next page.

Now we have PDP-8/I, PDP-11/20, PDP-11/40, PDP-11/70 and PDP-10/KI10.
Not to mention the PiDP8 replica and soon the PiDP11.

Joerg