Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Use '%zu' and '%zd' as appropriate for size_t / ssize_t.

Fixed missing or broken library dependencies.

Up the scale of the SPX loopback check a bit: use much larger data sizes
so that we need to do segmentation.

o style.Makefile(5): WARNS= -> WARNS?=.

Add spxabort, a simple netipx/spx regression test that triggers
pru_abort() by closing a listen socket while completed connections are
presenting in its listen queue. Unfortunately, it's difficult to
trigger the other two pru_abort() cases using user APIs, so they are
not covered by this test.

Add simple regression test to ping pong a data packet over SPX in stream
mode. Support both connection via connect() and sendto(), but don't
compile in sendto() for now, since netipx doesn't appear to actually
implement that (doh).

Add a simple IPX datagram regression test, which opens two IPX datagram
sockets, binds a local port, sends a datagram, and confirms that it is
received.

Add a short README with configuration hints to get the netipx regression
tests up and running. This is likely a message to myself in six months
when I've completely forgotten how.

Modify ipxsocket regression test to create and close sockets several
times, with variable length sleeps between socket() and close(). This
will help to ensure that IPX/SPX timers fire while the sockets are
open, and hence have PCB's on the IPX pcb list, so that if timers are
going to stumble over PCB types they don't expect, it will happen as
part of this test.

Add simple ipxsocket regression test: open, and close, various IPX socket
types supported by the FreeBSD netipx implementation.