This ROMWBW version is an extract of https://github.com/mecparts/zmp/bin
as at Aug 23rd, 2021.

- Overlay files must reside on default drive at time program is
  launched.  This seems to preclude the path search feature of
  ZSDOS/ZCPR which would be nice.  Need to look into this.
- Need some mechanism for user to select a CIO unit other than CIO 1
  without modifying and rebuilding application.
- Initialization messages refer to CIO 1 as CIO 0
- System hangs after error message if there is no CIO 1 unit
- When leaving program, terminal cursor remains hidden

--WBW 1:42 PM 8/23/2021

- When leaving program, terminal cursor remains hidden (fixed)
- System hangs after error message if there is no CIO 1 unit (fixed)
- Initialization messages refer to CIO 1 as CIO 0 (fixed)

--WBW 1:58 PM 8/23/2021

- Restore cursor on normal program exit.
- Revert original HBIOS conout and default console code as there
  is no associated facility for direct HBIOS conin.
- Allow setting port 0 and port 1 CIO device from command line
  ZMP 2 sets comms port to CIO 2. Can set primary and secondary
  i.e. ZMP 21 but only primary supported on this ZMP version.
  Untested on Ron Murrays ZMP15
- Space getting short so messages shortened. 

--PMS 8/24/2021