Add single-letter options for --version, --no-daemon, --debug, and
--pid-file (and document them, as well as the existing single-letter
option for --help).
https://bugzilla.gnome.org/show_bug.cgi?id=700550
When run with --no-daemon, NM used to duplicate all syslog output to
stderr, for ease of debugging. But this meant it had to tell systemd
to ignore stderr, so you wouldn't get duplicated log entries. But that
meant we lost error messages that didn't go through nm_log. (eg,
g_warning()s and g_return_if_fail()s).
Fix this by making --no-daemon no longer duplicate syslog output to
stderr, and removing the "StandardError=null" from the systemd service
file. To get the old behavior, you can use --debug instead of
--no-daemon.
https://bugzilla.gnome.org/show_bug.cgi?id=700550
DocBook is not my favorite thing in the world, but it's
<lots-of-emphasis>far</lots-of-emphasis> saner than troff. Some style
parts cribbed from systemd.
This is preparatory work for actually improving the content of the
man pages.