[clang] [Clang] Allow raw string literals in C as an extension (PR #88265)

[Aaron Ballman via cfe-commits]

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@@ -43,6 +43,9 @@ code bases.
 C/C++ Language Potentially Breaking Changes
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+- Clang now supports raw string literals in ``-std=gnuXY`` mode as an extension in
+  C. This behaviour can also be overridden using ``-f[no-]raw-string-literals``.
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AaronBallman wrote:

This should mention #85703 somewhere

https://github.com/llvm/llvm-project/pull/88265