Refs 13882. Fixes for _UNICODE macro on Visual Studio (backport #2510)

[mergify]

This is an automatic backport of pull request #2510 done by Mergify.
Cherry-pick of 49e7986 has failed:

On branch mergify/bp/2.1.x/pr-2510
Your branch is up to date with 'origin/2.1.x'.

You are currently cherry-picking commit 49e7986ff.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/cpp/utils/StringMatching.cpp

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   src/cpp/utils/SystemInfo.cpp

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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