We don't have temporary snapshots yet, and we probably never will have processes
that could exit.

It clashes with a macro of the same name in OSv.

OSv isn't ready for this yet.

Previously, we re-implemented "unsupported" file operations (e.g., chmod
for a pipe on which fchmod makes no sense) several times - there was
an implementation only for chmod in kern_descrip.c, used in sys_socket.c,
and af_local.cc had its own. As we add more file descriptor type (e.g.,
create_epoll()) we'll have even more copies of these silly functions, so
let's do it once in fs/unsupported.c - with the fs/unsupported.h header
file.

This also gives us a central place to document (and argue) whether an
unimplemented ioctl() should return ENOTTY or EBADF (I think the former).

getsockname() used to fail because by the time the call chain reached
kern_getsockname() it got addrlen=0. The problem is getsockname1()
which gives it an initialized local variable instead of the given
addrlen.

Most of these layers and copies are redundant, and are only left because
of previous incarnations of the code which had copies from user space -
but we need to at least get the unnecessary copies right ;-)

This allows to remove various #if 0'ed code using vnode_t or znode_t to be
compiled, both in the current headers and future ported code.

this haven't caused a real bug, I just noticed it while tracing.
it may be dangerous if in some flow, the stack will not be zeroed

read_random() is used indirectly by the TCP stack to randomize a local port number,
before this patch it was identical in each execution, and that caused NAT problems.

also add a FIXME note to implement real random one day.

the linux/musl definition is 2 bytes long instead of 1 byte as in
freebsd, this patch is fixing this issue which caused ifconfig to fail

Attempting to put an end to the linux<->freebsd confusion.