Fix struct io_iocb_vector padding for 32bit architectures

The io_iocb_vector structure definition is missing padding for @vec
and @nr, which results in -EINVAL being returned from io_submit() on
applications compiled for 32 bit architectures.  Fix it.

Signed-off-by: Brett Holman <bholman.devel@gmail.com>
[JEM: add commit message; use PADDEDul for nr]
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>

src/libaio.h

@@ -116,8 +116,8 @@ struct io_iocb_common {
 };	/* result code is the amount read or -'ve errno */
 
 struct io_iocb_vector {
-	const struct iovec	*vec;
-	int			nr;
+	PADDEDptr(const struct iovec *vec, __pad1);
+	PADDEDul(nr, __pad2);
 	long long		offset;
 };	/* result code is the amount read or -'ve errno */