[clang] [clang][test] Add test for comma operator rejection in preprocessor conditionals (PR #155570)

[Corentin Jabot via cfe-commits]

cor3ntin wrote:

@shafik was https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#3017 resolved ?

> > Should I move this to clang/test/CXX/drs/cwg1436.cpp and format it according to the DR test conventions?
> 
> Something like that yeah; I think there might already be a file that contains some of the 14XX tests somewhere but I’m not sure; I’ve tagged Vlad about this who should be able to tell you where exactly to put it.

Yes, please!

https://github.com/llvm/llvm-project/pull/155570