AngelScript compiler: Update to latest version, add support for OpenSR-only scripts.

[DaloLorn]

The benefits of updating to a newer version of AngelScript should be self-explanatory. However, in order to allow mods to be backwards-compatible with older builds of the game, we must allow them to block scripts out as "OpenSR-only". This will require some careful exploitation of loopholes in the current compiler.

• Upgrade to latest AngelScript.
  • IMPORTANT:: Set the asEP_PROPERTY_ACCESSOR_MODE compiler flag to 2, or all existing scripts will break! (See https://discord.com/channels/190112637307060225/513682262559293480/950713592326520832 for context.)
• Add a preprocessing step to the AngelScript compiler, executed before all other steps:
  • Remove all instances of //%, /*%, and %*/ from the script. (See https://discord.com/channels/190112637307060225/513682262559293480/950711109210501130 for context.)
  • Possibly add some sort of versioning behavior, so that subsequent changes to the script engine (like in game/mods/mod_manager: Add support for Launchpad's custom mod statuses. #9) don't require us to resort to increasingly absurd methods of blocking out old code? Maybe something like //%153, /*%153 and 153%*/ to denote the latest supported version of the script engine, with the compiler then skipping blocks with a version > 153? Or is it better to just demand that OpenSR users keep updating their game, since they're presumably already using the Launchpad? 🤔

This is a pretty big improvement, but it's possibly also a pretty big undertaking. It's not currently blocking any other tasks, so there's no pressing need for us to rush in with a "do it right now drop whatever else you're doing" mindset.