
GWTerm protocol definition:

  Global War sends "ESC GWEnq" and waits approx 1/4 second for a
  response from GWTerm.  If the response is not received, Global War
  assumes the player is not using GWTerm and will send ANSI maps.

  GWTerm responds with "ACK REV"

  Global War compares REV with the current rev level it supports.
  If REV is acceptable, Global War will reply with an "ACK" otherwise
  it will send a "NAK".

  GWTerm, if it does not receive an ACK, will notify the user by displaying
  the message "This copy of GWTerm is obsolete"

  Global War will send codes to tell GWTerm to display maps as follows:
      "ESC M 1"  display map of the Globe
      "ESC M 2"  display map of Africa
      "ESC M 3"  display map of Asia
      "ESC M 4"  display map of Australia
      "ESC M 5"  display map of Europe
      "ESC M 6"  display map of N. America
      "ESC M 7"  display map of S. America
  How GWTerm goes about displaying these maps is entirely optional.  In this
  version, screen dumps are stored in WAR.IMG and are read and block moved
  onto the screen RAM.  Graphics mode could also be used.  The main
  consideration is that country names, menus, and other data will be sent
  and must be printed on top of these maps at specified screen coordinates
  specified using ANSI codes.

  Global War will send "ESC Q" when the player exits the game to tell
  GWTerm to terminate and exit back to the terminal program (Telix, etc)

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