samedec-0.4.0: The Spring 2024 Update

Are you "Weather Ready?" This release is mostly compatible with
previous versions but adds more SAME codes and environment
variables.

ENHANCEMENTS

* Support the following new SAME codes:

  * EAN: Renamed to National Emergency Message
  * NAT: National Audible Test
  * NST: National Silent Test
  * FSW: Flash Freeze Warning
  * FZW: Freeze Warning
  * HLS: Hurricane Local Statement
  * SQW: Snow Squall Warning

* Discontinue the `SAMEDEC_SIGNIFICANCE` level of "`M`"
  (Message), which is not found anywhere in the standards
  document. The following messages are upgraded to
  Statement:

  * ADR: Administrative Message
  * NMN: Network Message Notification

* Improved detection of National Weather Service vs
  Environment Canada. samedec will no longer output a
  generic `SAMEDEC_ORIGINATOR` of "`Weather Service`."
  Instead, samedec will output either
  "`National Weather Service`" or "`Environment Canada`."

* New environment variables for child processes

  * `SAMEDEC_IS_NATIONAL`: "`Y`" for national activations;
    otherwise present but empty

  * `SAMEDEC_SIG_NUM`: a numeric representation of the
    significance level

* Add proper integration test scripts for child processes

FIXES

* IMPORTANT: Fix code entry for ADR (Administrative Message),
  which was previously wrong.

* Handle EOF within the main app. Child processes are now
  spawned even for very short input files.

* Update to Edition 2021

* Replace is-terminal with terminal_size