This is needed for forced unwind, for some testcases in
libunwind/libcxxabi.
This adds an aarch64 case for extracting the LanguageHandler and
HandlerData fields from unwind info, in UnwindCursor::getInfoFromSEH,
corresponding to the existing case for x86_64.
This uses the struct IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY_XDATA; this only
became available in WinSDK 10.0.19041.0 and mingw-w64 v11.0 (or a
mingw-w64 git snapshot after April 2023).
(This is only a build-time requirement though; the format for the unwind
data has been fixed since the start of Windows 10 on ARM64, so this
doesn't impose any runtime requirement.)
2e436b15d3