Allow FFI signatures with more than eight arguments #1030

Summary

Remove or raise the fixed eight-argument ceiling for bound native functions, with an ABI-driven limit instead of fixed Dispatch1* through Dispatch8* coverage.

Why

Raylib 6.0's DrawBillboardPro has nine parameters and is omitted solely because GocciaScript cannot express or dispatch it. The merged skip report records it as the one more-than-8-arguments exclusion.

Current behavior

On current main (34cc32f):

const lib = FFI.open("./fixtures/ffi/libfixture" + FFI.suffix);
lib.bind("get_answer", {
  args: ["i32", "i32", "i32", "i32", "i32", "i32", "i32", "i32", "i32"],
  returns: "i32",
});

Binding throws:

FFI supports a maximum of 8 arguments

Current-source evidence:

• MAX_FFI_ARGS is hard-coded to 8.
• Function signature parsing rejects a ninth argument.
• The native dispatcher has fixed cases only through eight arguments.
• The public FFI reference documents the limit.

The fresh-main FFI suite passes in interpreted and bytecode modes (92 tests, 337 assertions), including the existing test that treats nine callback arguments as invalid.

Expected behavior

A nine-argument native signature should bind and call correctly on supported ABIs. Define a defensible implementation cap if an unbounded descriptor is not practical, and keep function/callback limits consistent where they share the same call-frame machinery.

Scope notes

• Initial integration coverage should include a real nine-argument fixture and the raylib DrawBillboardPro shape.
• This issue does not require automatic C header parsing.
• Related: Add explicit FFI support for native shared libraries #178, FFI v2 #827, and GocciaScript-Raylib PR #7.