[llvm] [llvm-objdump] Implement decoding auxiliary header for xcoff with llvm-objdump --private-headers (PR #105682)

[zhijian lin via llvm-commits]

diggerlin wrote:

> Sorry for the delay in reviewing again. A few more small comments and then I think we're done.

No need to apologize; thank you very much for your professional feedback!

https://github.com/llvm/llvm-project/pull/105682