Narrative switching support

[nsensfel]

• Add the following instructions:
  • (narrative:push filename tag_list) which creates a new memory stack and loads the indicated narrative.
  • (narrative:pop) which pops the current narrative (frees memory too).
  • (narrative:pop_until_any tag_list) which pops narrative until there is a narrative with at least one tag in the tag_list.
  • (narrative:pop_until_all tag_list) which pops narrative until there is a narrative with all the tags in the tag_list.
  • (narrative:pop_while_any tag_list)
  • (narrative:pop_while_all tag_list)
  • (narrative:switch filename tag_list) which pops the current narrative and pushes the new one.
  • (narrative:add_tag tag)
  • (narrative:remove_tag tag)
• Add the following computation:
  • (narrative:tag_list)
• Add the shared variable category of issue https://github.com/nsensfel/tonkadur/issues/20. They are stored separately as they do not get freed when narrative switch.
• Addresses should reflect the narrative memory stack system.

Example of things that could use separate narratives:

• Menus.
• Instantiated areas (random dungeon).