[llvm] [llvm-readobj] enable demangle option for the xcoff object file (PR #78455)

[James Henderson via llvm-commits]

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@@ -61,6 +61,11 @@ file formats.
  Display demangled symbol names in the output; the option only is for ELF and
  XCOFF file format.
 
+.. option:: --no-demangle (default)
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jh7370 wrote:

Options are listed in this document in alphabetical order (so this belongs after `--needed-libs`.

Also, `(default)` doesn't belong in the option title, but instead should be listed in the text of the description as a new sentence, e.g. "Enabled by default." at the end.

https://github.com/llvm/llvm-project/pull/78455