[clang-tools-extra] Fix #35272: Don't replace typedefs in extern c scope (PR #69102)

[Piotr Zegar via cfe-commits]

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@@ -28,6 +28,15 @@ After:
   using R_t = struct { int a; };
   using R_p = R_t*;
 
+The checker ignores `typedef` within `extern "C" { ... }` blocks.
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PiotrZSL wrote:

I think so, for example I would like to enable this for my projects.
Ignoring extern "C" makes only sense if same header is compile in C and C++ mode.
If header is compiled only in C++ mode, but uses extern "C" simply to properly handle symbols mangling, then there is no need to ignore such typedefs.

https://github.com/llvm/llvm-project/pull/69102