- 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

Add a short regression test to try to exercise races in the non-atomic
nature of implied connect via sendto(). Oddly, uipc_usrreq.c implements
this for stream sockets, but doesn't set the flag in its protocol
definition so that it can actually be used. As such, the stream test is
implemented but doesn't run for now.