Log Message:
forth-retro: Update to 2019.7

Changelog:
# RETRO 2019.7

This is the changelog for the development builds of Retro.
The version number is likely to change; I'm targetting an
early July window for this release.

## Bug Fixes

- all
  - strl* functions now renamed, included on all builds
  - `d:add-header` is extended by retro.forth to remap
    spaces back to underscores when creating headers
  - fix overflow issue with `n:MIN`, `n:MAX`
- build
  - fix compile issue under Solaris
- retro-unix
  - `clock:year` corrected
  - `clock:month` corrected
- examples
  - fixed issue in mail.forth

## Build

- Merged Linux & BSD Makefiles

## Core Language

- new words
  - `a:fetch`
  - `a:store`
  - `s:replace-all`
- renamed
  - `a:nth` to `a:th`
  - `v:update-using` to `v:update`
- performance improvements
  - `times`
  - `times<with-index>`
  - `while`
  - `until`

## Documentation

- merged BSD, Linux, macOS build instructions
- updated Starting instructions
- added implementation notes on arrays
- updated the initial word table in rx.muri
- added a man page for retro-describe

## Toolchain

- fixed a bug in the glossary server

## Examples

- new examples
  - bury.forth
  - compat.forth
  - gopher.forth
  - magic-8th-ball.forth
  - mandelbrot.forth
  - RFC865.forth
  - RFC867.forth
  - safety-net.retro
  - shell.forth
  - sqlite3 wrapper
  - unix-does-user-exist.forth
- improved examples
  - 99bottles.forth
  - edit.forth
- other
  - publish-examples.forth now uses `retro-document`
    to generate glossaries

## General

- reorganized directory tree

## I/O

- retro-unix (rre)
  - added `clock:utc:` namespace
  - remove gopher downloader
  - add sockets interface
  - add `unix:slurp-pipe`

## Interfaces

- retro-compiler
  - runtime now supports scripting arguments
- retro-unix
  - remove FullScreenListener
  - ok prompt now a hook
  - rewrite the listener
- retro-c#
  - restored this to the source tree
- native
  - better `0x` prefix handling

## Notes for the future:

In a future release, the examples will start using a `.retro`
file name extension rather than `.forth` to avoid possible
confusion with other systems that use `.forth` (e.g., MPE).