Fix some OS/8 directory handling routines which did not correctly handle
directories with optional extended words. Add missing
RL01 initialization support for RT11.
Just tried to build fsio on FreeBSD and found it complaining about
unknown functions letoh32. Turns out that the attempt to make this
portable to FreeBSD is incorrectly assuming that FreeBSD should be
like NetBSD, when in fact it is more like OpenBSD in this regard.
Moving the defined(__FreeBSD__) so it selects the same block as
__OpenBSD__ makes fsio build correctly on FreeBSD 11 (and presumably
later).
