- 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 libutempter compatibility interface to libulog.

The ulog_login_pseudo(3) and ulog_logout_pseudo(3) interfaces provide a
functionality identical to what libutempter has to offer. Just transform
libutempter's calls into the before mentioned functions.

libutempter doesn't work with utmpx, so instead of fixing I thought the
easiest way would be to integrate this functionality. libutempter is
used by applications like xterm and the KDE libraries, so if I ever
change the underlying file format, these applications will keep working
automatically.

Also increase __FreeBSD_version to indicate the addition (as well as the
import of libulog).