Ever closer to z4 game support

This update repairs a lot of things necessary to bring z4 game support to Status Line. For the initial versions, I cut a few corners here and there as part of my general exploration of, "Will this project even be feasible?" Now, to continue building the functionality of Status Line I had to implement a number of complex functions which were optional/unused in z3 games, but are mandatory for z4/5 games.

v1.2 Changelog

Future-proofing

• Split-screen function implemented. This is a requirement for z4/5 games; but can be enjoyed in z3 Seastalker, shown.
  
• 30% lower Pico-8 RAM usage (need to use memory efficiently with larger v4/5 games)
• Better implementation of z-machine RAM (to handle 256K game imports)
• Implemented low/high tone beep "sound effects"
  
• (for anyone looking at the code, some v4/5 ops are implemented, waiting for their day to shine)
  

Bug fixes

• A true, full screen of text (see the difference here in The Witness)
  Previously, I relied on Pico-8 default screen scrolling but always "lost" one line of output at the bottom of the screen. The new screen handling routines, needed for split-screen, regain this lost line.
     
• Numeral-only input now works; ex. Lurking Horror "login" at start of game
• Faster feedback to player input

Coming headaches

Adding z4 support means supporting Trinity and A Mind Forever Voyaging, both of which assume a 40-character wide screen. Some things in those games simply will not look right on a Pico-8's 32-character screen; there's no getting around that issue. However, those items tend to be interstitial quotes and other flavour text, things that are not particularly essential to the gameplay proper. In general, the Pico-8 screen size presents a challenge to delivering a quality experience for more recent games. I'll just take it one step at a time.

Quicky update

I've achieved "first text to screen" in the z4 game Nord & Bert Couldn't Make Head or Tail of It. Feels good to see visual confirmation I'm on the right track.