MONIT - lightweight ATSIGN HACTRN replacement.

Jack Haverty wrote on its-hackers:

> On MIT-DM, the most commonly used top-level program was called
> "monit". It was used by most people instead of DDT because it required
> less memory, which was a very scarce and precious commodity in the
> early 70s before paging and swapping.  In fact there was a lot of peer
> pressure to use monit unless you had a very good reason to use DDT.

This is a very old source file -- AI: SYSENG; MONIT 114 is listed in
MAPS in 1971-04. Development happened on DM; "Scenarios for Using
Arpanet at the International Conference on Computer Communication" has a
1972-09 transcript showing MONIT 192 on DM.

The binary SYS; TS MONIT is listed on AI, MC and ML from 1971 to 1983 in
MAPS, although it doesn't survive in the AI/MC KS10 dumps. A 1981
message to BUG-ITS from ED@MIT-ML suggests it was an old version:

> ML:SYS;TS MONIT [...] does not have symbols nor the correct start
> address (1300). It is pretty badly broken, but great fun to play with
> nevertheless.

doc/programs.md

@@ -143,6 +143,7 @@
 - MLDEV/MLSLV, allows access to remote systems as devices (e.g. DB:).
 - MLIFE, Mike Speciner's Conway Life.
 - MODEMS, modems dragon.
+- MONIT, lightweight ATSIGN HACTRN replacement without debugging support.
 - MSEND, send to many users.
 - MSPLIT, split a file into smaller parts.
 - MTBOOT, make bootable tapes.