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

[Ben Langmuir via cfe-commits]

benlangmuir wrote:

> I assume that @benlangmuir added the scanner unit-test to demonstrate the current behavior instead of trying to make sure it's preserved.

Correct.  They're only interesting to the scanner insofar as they're used in `_Pragma()` as far as I know. If we can handle them, great!  You just need to update the test expectations for those cases.

Thanks for working on this!

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