Fix a warning (on cygwin) to allow -Werror

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-fast-export.c

@@ -417,7 +417,8 @@ static void export_marks(char *file)
 	for (i = 0; i < idnums.size; i++) {
 		if (deco->base && deco->base->type == 1) {
 			mark = ptr_to_mark(deco->decoration);
-			fprintf(f, ":%u %s\n", mark, sha1_to_hex(deco->base->sha1));
+			fprintf(f, ":%"PRIu32" %s\n", mark,
+				sha1_to_hex(deco->base->sha1));
 		}
 		deco++;
 	}