http: mark unused parameter in fill_active_slot() callbacks

http: mark unused parameter in fill_active_slot() callbacks

We have a generic "fill" function that is used by both the dumb http
push and fetch code paths. It takes a void parameter in case the caller
wants to pass along extra data, but (since the previous commit) neither
does so.

So we could simply drop the extra parameter. But since it's good
practice to provide a void pointer for in callback functions, we'll
leave it here for the future, and just annotate it as unused (to appease
-Wunused-parameter).

While we're marking it, let's also fix the type in http-walker's
function to have the correct "void" type. The original had to cast the
function pointer and was technically undefined behavior (though
generally OK in practice).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>