[COMMITTED] Fix test-skeleton C99 designed initialization

[Paul Eggert]

Adhemerval Zanella wrote:
> -  struct timespec remaining = {};
> +  struct timespec remaining = { 0 };

I suggest appending a comma; this style is often used in GNU apps as a cue to 
the reader that the remaining zeros are elided. Like this:

    struct timespec remaining = { 0, };