[clang] [clang-format] Add SpaceBeforeUnderscoreParens option for GNU gettext… (PR #159925)

[via cfe-commits]

owenca wrote:

I would add `SBPO_GNU`:
```
SpaceBeforeParens:
  GNU # same as Always except when preceded by an underscore as the function name
```

https://github.com/llvm/llvm-project/pull/159925