[Simh] Zork update

[Lars Brinkhoff]

Since MDL Zork is part of the SIMH software kits, you may be interested
to know I have been given a version that is newer than the one from Bob
Supnik.  Most files are identical (or just have some end-of-fie ^C's
added), but a few have minor updates.

Check out the zork (Spunik) and zork2 (updated) directories here:
https://github.com/PDP-10/its/tree/lars/zork/src

Oh, and related to this, we now have PDP-10 Muddle sources.  It should
build for TOPS-20, but the ITS support has rotted.