Add a mechanism for libraries to resolve incompatibilities between
library versions before linking.
This is currently used for ChipmunkSpriteEngine and GoatGUIEngine,
where early versions used integer IDs when loading CGs (later versions
use strings).
asset_exists and asset_get now take 1-indexed IDs.
Custom CG indexing code for Shaman's Sanctuary is now removed and
replaced with a proper implementation of afa v1 archives in libsys4.
Refactor GoatGUIEngine into various files under src/parts/.
The external interface to this code is the functions prefixed with PE_
and generally following the naming of the HLL functions which they
implement.
The reason for this is that there are multiple HLL libraries that
implement more or less the same GUI interface (GoatGUIEngine, GUIEngine
and PartsEngine).
Also added here are a number of miscellaneous stubbed-out HLL functions
that are used by Rance 01 (which now runs up to the point where it tries
to create the title menu).
Used in Shaman's Sanctuary. Mostly identical to StoatSpriteEngine, but
with a few additions and some removed functions (notably, the
MultiSprite functions were removed).