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

Fix whitespace inconsistencies found in homegrown Symbol.maps.

Remove utmpx stub from libulog.

I'm not increasing the shlib major version for this, because not a
single application outside the base system should have used these
functions in such a short timespan.

Rewrite ulog_login(3) and ulog_logout(3) to build on top of the utmpx
implementation in libc.

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).

Massively extend libulog:

- Just like struct utmp, store strings inside struct utmpx itself. This
is needed to make things like pututxline() work.
- Add ut_id and ut_pid fields, even though they have little use in our
implementation.
- It turns out our "reboot" wtmp entries indicate a system boot, so
remove REBOOT_TIME
- Implement getutxline() and pututxline
- Add getutxuser() and setutxfile(), which allows us to crawl wtmp and
lastlog files as well.
- Add _ULOG_POSIX_NAMES, so we can already use the POSIX names if we
really want to.

Add a new library: libulog.

One of the things I really want to do, is to get rid of the limitations
of our current utmp(5) mechanism:

- It only allows 8 byte TTY device names.
- The hostname only allows 16 bytes of storage.

I'm not a big fan of <utmpx.h>, but I think we should at least try to
add parts of it. Unfortunately we cannot implement <utmpx.h>, because we
miss various fields, such as ut_id, ut_pid, etc. The API provided by
libulog shares some similarities with <utmpx.h>, so it shouldn't be too
hard to port these applications eventually. In most simple cases, it
should just be a matter of removing the ulog_ prefix everywhere.

As a bonus, it also implements a function called ulog_login_pseudo(),
which allows unprivileged applications to write log entries, provided
they have a valid file descriptor to a pseudo-terminal master device.

libulog will allow a smoother transition to a new file format by adding
a library interface to deal with utmp/wtmp/lastlog files. I initially
thought about adding the functionality to libutil, but because I'm not
planning on keeping this library around forever, we'd better keep it
separated.

Next items on the todo list:

1. Port applications in the base system (and ports) to libulog, instead
of letting them use <utmp.h>.
2. Remove <utmp.h>, implement <utmpx.h> and reimplement this library on
top.
3. Port as many applications as possible back to <utmpx.h>.