[clang] [clang-repl] Ensure clang-repl accepts all C keywords supported in all language models (PR #142749)

[Anutosh Bhat via cfe-commits]

anutosh491 wrote:

Should help us in the long run and fix the errors we see while including input/output based header on xeus-cpp-lite (happens cause these internally reference `_Noreturn` that clang-repl currently fails to understand)

![image](https://github.com/user-attachments/assets/d5da48bf-5fd0-4310-853b-9a5c82f9f231)


https://github.com/llvm/llvm-project/pull/142749