`getfsstat` v.s. `getvfsstat` condition is different than
`statfs` v.s. `statvfs`, so split each condition and simplify.
For `get(v)fsstat` side, changed to check and use `getmntinfo`, because
it is better than `get(v)fsstat` with fixed buffer size, and easier
than improve it with dynamic buffer allocation.
Signed-off-by: OBATA Akio <obache@wizdas.com>
NetBSD APM is supported other than i386 too, emulate API,
so change to detect with MI support header.
Additionally, catch up support codes to others.
Signed-off-by: OBATA Akio <obache@wizdas.com>