patchhelp.c: mark a file-local function static

>
> Commit 4f671d74 ("help: respect new common command grouping",
> 18-05-2015) adds the 'cmd_group_cmp' funtion as an external
> symbol.
>
> Noticed by sparse. ("'cmd_group_cmp' was not declared. Should it
> be static?")
>
> Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
> ---
>
> Hi Sebastien,
>
> If you need to re-roll the patches in your 'sg/help-group' branch,
> could you please squash this into the relevant patch (commit 4f671d74).
>
> Thanks!
>
> ATB,
> Ramsay Jones
>
>   help.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/help.c b/help.c
> index 71027b7..7881ab7 100644
> --- a/help.c
> +++ b/help.c
> @@ -218,7 +218,7 @@ void list_commands(unsigned int colopts,
>   	}
>   }
>
> -int cmd_group_cmp(const void *elem1, const void *elem2)
> +static int cmd_group_cmp(const void *elem1, const void *elem2)
>   {
>   	const struct cmdname_help *e1 = elem1;
>   	const struct cmdname_help *e2 = elem2;
>