Cosmetic change, use the same union name on the left and right sides
of the conversion.

Tested by:	Petr Salinger <Petr.Salinger@seznam.cz>
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Fix several warnings.
Fix crash in aio_pty_cleanup() by initializing the pointer before
dereferencing.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week