Document varadic args as int, since you can't have short varadic args (they are

promoted to ints).

- `mode_t` is `uint16_t` (`sys/sys/_types.h`)
- `openat` takes variadic args
- variadic args cannot be 16-bit, and indeed the code uses int
- the manpage currently kinda implies the argument is 16-bit by saying `mode_t`

Prompted by Rust things: https://github.com/tailhook/openat/issues/21
Submitted by: Greg V at unrelenting
Differential Revision: https://reviews.freebsd.org/D21816

lib/libc/sys/mq_open.2

@@ -133,7 +133,7 @@ Create a message queue.
 It requires two additional arguments:
 .Fa mode ,
 which is of type
-.Vt mode_t ,
+.Vt int ,
 and
 .Fa attr ,
 which is a pointer to an

lib/libc/sys/open.2

@@ -61,7 +61,7 @@ In this case
 and
 .Fn openat
 require an additional argument
-.Fa "mode_t mode" ,
+.Fa "int mode" ,
 and the file is created with mode
 .Fa mode
 as described in