Add structured version info for pyexpat

Feature or enhancement

pyexpat.EXPAT_VERSION (from XML_ExpatVersion()) and pyexpat.version_info (from XML_ExpatVersionInfo()) describe the Expat library loaded at runtime: both functions are compiled into libexpat from its XML_MAJOR_VERSION, XML_MINOR_VERSION and XML_MICRO_VERSION macros. The same macros evaluated in pyexpat.c give the version of the headers the module was built against, which is what the #if XML_COMBINED_VERSION >= ... checks in the module depend on. The two can differ when a system libexpat is used. The build-time version is not exposed to Python; it can only be inferred from which parser methods exist.

Add pyexpat.VERSION_INFO for the build-time version, and make pyexpat.version_info a named tuple.

Linked PRs

• gh-157474

Expat のバージョンマクロと実行時バージョン API が公開されている pyexpat.c から始めます。既存の VERSION_INFO と version_info の定義を追い、そのうえで、ビルド時のバージョンが別々に公開されていることと、version_info が名前付きタプルとして振る舞うことを確認します。利用可能であれば pyexpat API のテストを確認し、両者が異なる場合に、両方のバージョンが正しく報告されることを確認します。