Remove all void-pointer arithmetic.

ANSI C99 doesn't allow void-pointer arithmetic. This patch fixes this in
various ways. Usually the strategy that required the least changes was used.

Signed-off-by: Florian Forster <octo@verplant.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

http-push.c

@@ -196,7 +196,7 @@ static size_t fwrite_sha1_file(void *ptr, size_t eltsize, size_t nmemb,
 	struct transfer_request *request = (struct transfer_request *)data;
 	do {
 		ssize_t retval = write(request->local_fileno,
-				       ptr + posn, size - posn);
+				       (char *) ptr + posn, size - posn);
 		if (retval < 0)
 			return posn;
 		posn += retval;