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>

diff.c

@@ -515,7 +515,7 @@ static void emit_binary_diff(mmfile_t *one, mmfile_t *two)
 		else
 			line[0] = bytes - 26 + 'a' - 1;
 		encode_85(line + 1, cp, bytes);
-		cp += bytes;
+		cp = (char *) cp + bytes;
 		puts(line);
 	}
 	printf("\n");