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.

Add includes where needed, remove duplicate definitions

the lack of extern "C").

This is a way to sleep without a wakeup channel.

I had to rename the symbol to bsd_pause because it conflicts with the classic
Unix pause syscall exposed through unistd.h via libcstd++.

NET_RT_IFLIST (list interfaces) and NET_RT_DUMP (dump rout entries).

This flag implies the created thread is not started, but we currently
always start it. In addition the thread_lock/sched_add/thread_unlock
mess the BSD code usually does is something we'd rather avoid for now.

Linux IOCTL commands in addition to the BSD IOCTLS. Linux IOCTLs should be
used instead of BSD IOCTLs whenever possible.

Added support for passing bsd commands to setsockopt() by negating the bsd cmd values. This is guarnteed NOT to clash with Linux commands.