windows-rdl more complete GUID parsing

[kennykerr]

Fixes: #4584

[Copilot]

✅ Ready to approve

The change is well-scoped, preserves prior behavior via a fallback path, and adds a targeted regression fixture for the reported macroized GUID parsing failure.

Note: this review does not count toward required approvals for merging.

Pull request overview

Improves windows-rdl’s clang-based extraction of IID_ GUIDs by handling macroized GUID initializers (e.g., the 7zip SDK pattern) via AST constant evaluation, and adds a dedicated fixture to prevent regressions.

Changes:

• Parse IID_ GUID variable initializers via libclang AST evaluation (clang_Cursor_Evaluate) with a token-based fallback.
• Add Cursor::evaluate_unsigned() helper to safely evaluate integer constant expressions.
• Add a new clang fixture (iid_var_macroized) covering macro-expanded GUID initializers and expected RDL output.

File summaries

File	Description
crates/libs/rdl/src/clang/mod.rs	Adds AST-based GUID initializer parsing for IID_ variables with fallback to the existing token-based parser.
crates/libs/rdl/src/clang/cx.rs	Introduces Cursor::evaluate_unsigned() to read evaluated integer constants from libclang.
crates/tests/libs/bindgen/data/clang/iid_var_macroized/input.h	New fixture input modeling macroized GUID variable declarations (7zip-style).
crates/tests/libs/bindgen/data/clang/iid_var_macroized/expected.rdl	New golden output validating correct GUID extraction from macroized initializers.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 0

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