WIP: Implement GRFv9

[PeterN]

Motivation / Problem

GRFv9

Description

• ALL existing Extended Byte fields are now Word fields.
• Action 0:
  • num-info is now a Word.
• Action 2:
  • set-id is now a Word.
  • subroutine is now a Word.
  • parameter is now a DWord.
  • VariationalAction2 nvar is now a Word.
  • RandomAction2 nrand is now a Word.
• Action 3:
  • n-id is now a Word.
  • ids... are each now a Word.
  • num-cid is now a Word.
  • cargo-type is now a Word.
• Action 4:
  • num-ent is now a Word.
  • offset is now always a Word, instead of varying depending on feature/flags.
• Action 7/9:
  • num-sprites is now a Word. If bit 15 is set, then this is a label instead of the number of sprites.
• Action A:
  • num-sets is now a Word.
  • num-sprites is now a Word.
• Action E:
  • num is now a Word.
• Action 10:
  • label is now a Word. Labels MUST have bit 15 set. This means there is no longer any conflict with labels overlapping numbers.
• Action 12:
  • num-def is now a Word.
  • num-char is now a Word.
  • base-char is now a DWord. This allows custom glyphs between 0x10000 and 0x1FFFFD to be defined.
• Action 13:
  • num-ent is now a Word.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, game_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker