[Bug c/107942] [10/11/12/13 Regression] Documentation of the volatile style for noreturn is gone and const style for const attribute is gone

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107942

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is the sample program to prove that const is still handled like const
attribute:
```
typedef int voidfn (void);

const voidfn constt;
[[gnu::noipa]]
int constt(void) {return 1;}

int f(void)
{
    return constt()+constt();
}
```