Differences from AI's TS FACTOR:
- KL10 define to put the TEST inner loop code at 100 rather than in the
registers -- ";;KL10 RUNS SLOWER IN ACS".
- Lookup table for commands, including uppercase and lowercase.
- A new "quit" command.
- Mixed-case messages.
- System calls modernised a bit; .CALL /OPEN/ rather than .SUSET/.OPEN,
and not opening the TTY in DDT mode.