Fixs: https://github.com/llvm/llvm-project/issues/145250. This PR makes clang accept single variadic parameter function declarator in type name. Eg. ```c int va_fn(...); // ok // As typeof() argument typeof(int(...))*fn_ptr = &va_fn; // ok // As _Generic association type int i = _Generic(typeof(va_fn), int(...):1); // ok ``` Signed-off-by: yronglin <yronglin777@gmail.com>