Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Switch to our preferred 2-clause BSD license.

Approved by: bp

Refactor select to reduce contention and hide internal implementation
details from consumers.

- Track individual selecters on a per-descriptor basis such that there
are no longer collisions and after sleeping for events only those
descriptors which triggered events must be rescaned.
- Protect the selinfo (per descriptor) structure with a mtx pool mutex.
mtx pool mutexes were chosen to preserve api compatibility with
existing code which does nothing but bzero() to setup selinfo
structures.
- Use a per-thread wait channel rather than a global wait channel.
- Hide select implementation details in a seltd structure which is
opaque to the rest of the kernel.
- Provide a 'selsocket' interface for those kernel consumers who wish to
select on a socket when they have no fd so they no longer have to
be aware of select implementation details.

Tested by: kris
Reviewed on: arch

/* -> /*- for license, minor formatting changes

Catch up with KSE changes.

Reviewed by: tjr

Major update of NCP requester:

Use mchain API to work with mbuf chains.

Do not depend on INET and IPX options.

Allocate ncp_rq structure dynamically to prevent possible stack overflows.

Let ncp_request() dispose control structure if request failed.

Move all NCP wrappers to ncp_ncp.c file and all NCP request processing
functions to ncp_rq.c file.

Improve reconnection logic.

Misc style fixes.

Forward declare some structs so that this header is more self-suifficent.

Update to version 1.3.4 of ncplib. Cleanup header files.

Import kernel part of ncplib: netncp and nwfs

Reviewed by: msmith, peter
Obtained from: ncplib