Bangle.js cutting edge (2v24.131 and later) speed improvements

Hi! I've been putting a bunch of work into optimisations on Espruino/Bangle.js lately, and I've done a bunch of stuff with the latest builds.

You'll find that writes to 1/2/4 bit offscreen buffers are a lot faster now, built-in JS functions now execute a lot faster (we're able to skip a 'parsing' step, and we also store them pretokenised), and for Bangle.js 2 specifically I've now built in the Layout library (you'll have to reinstall any apps that use Layout for the app loader to realise your Bangle has layout and upload your apps without their own version).

Not that the change is massive, but with a totally 'factory reset' watch with android installed the load times are as follows:

Bangle.js 2v24

• Anton clock 246ms
  
• load("messagegui.app.js") 329ms with read message
  
• load("messagegui.app.js") 331ms with unread message
  
  

2v24.128

• Anton clock 241ms
  
• load("messagegui.app.js") 271ms with read message
  
• load("messagegui.app.js") 308ms with unread message
  
  

So we manage to be 10% faster when viewing messages, and any app that uses setUI/showMenu/Layout/etc should be a lot snappier.