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).
The parts list is now a tree, and only a single sprite is registered in
the global scene. GoatGUIEngine now manages rendering order of its own
sprites internally.
Create a separate interface for managing the scene. The sact_sprite
interface is implemented on top of this, as is GoatGUIEngine (which is
now independent of sact_sprite).
This will allow more specialized graphics interfaces to be implemented
without adding to the complexity of the sact_sprite interace. (For
example, GoatGUIEngine needs to store multiple textures per sprite for
button states; this is not supported by sact_sprite.)
Nunuhara Cabbage