[PATCH] io: Check at runtime if timestamp supports nanoseconds

[Paul Eggert]

On 3/29/21 10:43 AM, Adhemerval Zanella via Libc-alpha wrote:

> +    printf ("warning: timestamp with nanoseconds not supportted\n");

supportted -> supported

I see you installed the patch already, so I took the liberty of 
installing the trivial spelling fix.