- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

Style: NO_MAN doesn't need any value.

Use WARNS?= instead of WARNS= in Makefiles so that global warning
settings can override local ones.

Pointed out by: ru

Start the dreaded NOFOO -> NO_FOO conversion.

OK'ed by: core

Add a small regression test that opens a TCP socket, listens on it,
performs a non-blocking connect from another socket, and then closes
the listen socket rather than accepting. This is intended to
exercise the close path in which connections are aborted due to a
close on the listen socket while the connection is in the listen
queue.