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.

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

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.