[clang] [clang][Sema] Add bounds checking for libc poll (PR #177286)

[Colin Kinloch via cfe-commits]

ColinKinloch wrote:

I've updated the branch to:
* Not use `mode_t` in clang
* Not use `std::optional` to hold the values of `O_CREAT` (The check wouldn't be valid if they were set to 0 anyway)
* Add missing test cases to trigger the too many arguments case
* Disable the `incorrect-libc-use` warning in select static analyser test cases

Is there a way to disable these warnings for the static analyser tests globally?

https://github.com/llvm/llvm-project/pull/177286