ZDE 1.6 (Z-System Display Editor) reconstituted source

Using the source code of VDE
2.67
as a guide, I've reconstituted the source code for ZDE 1.6.

The source has been assembled with:

• Al Hawley's ZMAC: assemble as is.
• MicroSoft's M80: rename to ZDE16.MAC, un-comment the first two lines
  and assemble. Use RELHEX to create ZDE16.HEX.
• ZASM (Cromemco's ASMB): Rename to ZDE16.Z80 and assemble. Use RELHEX
  to create ZDE16.HEX.

Use MLOAD to create ZDE16.COM.

There are still a couple of routines new to ZDE that I haven't figured
out (yet). But most of them have been sussed out.

ZDE 1.7

I've fixed the "doesn't preserve timestamps for files larger than a
single extent under ZSDOS" bug that was present in v1.6. The existing
ZDENST16.COM program will work with the 1.7 to set the program up for
your terminal and printer.