GitLab

Ursula. Quite a hairy code merge really, so let's hope it is
worth it to someone. What you get (back after 2 or 3 years):
- much more efficient for largish numbers of DAs (relevance
  to current build = approx 0)
- fancy reason codes to support fast update of
  Switcher bar display (relevance = 0)
- support for clamped maximum area sizes, to avoid address
  space exhaustion with big memory (relevance = 0)
- better implementation of shrinkable DAs, performance
  wise (if lots of DAs, relevance = approx 0)
- support for 'Sparse' DAs. Holey dynamic areas, Batman!
  (relevance, go on someone use the darned things)
Moderately development tested on HAL/32bit ARM9 desktop.
Note the Switcher should be compiled to use the new
reason codes 6&7, for fabled desktop builds.

Also, during this work, so I could see the wood for the
trees, redid some source code clean up, removing pre-Medusa
stuff (like I did about 3 years ago on Ursula, sigh). That's
why loads...