Colossal Cave Adventure v4.2

Changes

• Update README and manual to focus on the story and game, the origin
  has its own place and need not be repeated everywhere. Lead with
  the classic game intro.
• Update maintainer surname and project name: advent4 -> adventure
• Add map.jpg from https://rickadams.org/adventure/e_downloads.html
• Add Dockerfile and auto-builder for tiny containers
• Shrink stack usage for gettrav()
• Log save game filename in error and status messages

Fixes

• Fix out-of-bounds problems reported in issue #2
  • Some of these fixes affect game play, e.g. moving things should now
    actually work, in particular for "odd" objects. (What isn't odd in
    the Colossal Cave?)
• Fix lots of other out-of-bounds issues found by Coverity Scan
• Use SEEK_SET with fseek() instead of 0
• Fix missing game data when built with --disable-builtin