[PATCH] chg: silence warning of unused parameter 'sig'

[Jun Wu]

This looks good to me. Sorry for my careless. I actually noticed the issue
after sending the patch.

Alternative to the GNU extension "__attribute__", there are 2 common
patterns to silence the warning:

  void handlechildsignal(int /* sig */)

or in the body of the function:
  
  (void)sig;

Excerpts from Yuya Nishihara's message of 2016-06-28 23:30:13 +0900:
> # HG changeset patch
> # User Yuya Nishihara <yuya at tcha.org>
> # Date 1467121146 -32400
> #      Tue Jun 28 22:39:06 2016 +0900
> # Node ID 6092992b98fa30d9ea30e0a05f4a7682b99862c6
> # Parent  7dce56174916e09be39c690278942b4f7567b3f6
> chg: silence warning of unused parameter 'sig'
> 
> diff --git a/contrib/chg/chg.c b/contrib/chg/chg.c
> --- a/contrib/chg/chg.c
> +++ b/contrib/chg/chg.c
> @@ -381,7 +381,7 @@ error:
>      abortmsgerrno("failed to handle stop signal");
>  }
>  
> -static void handlechildsignal(int sig)
> +static void handlechildsignal(int sig UNUSED_)
>  {
>      if (peerpid == 0 || pagerpid == 0)
>          return;
> diff --git a/contrib/chg/util.h b/contrib/chg/util.h
> --- a/contrib/chg/util.h
> +++ b/contrib/chg/util.h
> @@ -12,8 +12,10 @@
>  
>  #ifdef __GNUC__
>  #define PRINTF_FORMAT_ __attribute__((format(printf, 1, 2)))
> +#define UNUSED_ __attribute__((unused))
>  #else
>  #define PRINTF_FORMAT_
> +#define UNUSED_
>  #endif
>  
>  void abortmsg(const char *fmt, ...) PRINTF_FORMAT_;