x64-windows: Fix extraction of chained UNWIND_INFO

[Joel Brobecker]

Hello,

I just pushed the following 2 patches:

  *  [PATCH 1/2] x64-windows: Fix extraction of chained UNWIND_INFO
     This one fixes an issue processing a function's chained unwind info.

  *  [PATCH 2/2] Add debug trace in
     This one adds a trace that I would have found useful while
     investigating the issue.

Tested on x86_64-windows using AdaCore's testsuite.

Thank you,
-- 
Joel