The original version of virTimeLocalOffsetFromUTC() would fail for
certain times of the day if daylight savings time was active. This
could most easily be seen by uncommenting the TEST_LOCALOFFSET() cases
that include a DST setting.

After a lot of experimenting, I found that the way to solve it in
almost all test cases is to set tm_isdst = -1 in the struct tm prior
to calling mktime(). Once this is done, the correct offset is returned
for all test cases at all times except the two hours just after
00:00:00 Jan 1 UTC - during that time, any timezone that is *behind*
UTC, and that is supposed to always be in DST will not have DST
accounted for in its offset.

I believe that the code of virTimeLocalOffsetFromUTC() actually is
correct for all cases, but the problem still encountered is due to our
inability to come up with a TZ string that properly forces DST to
*always* be active. Since a modfication of the (currently fixed)
expected result data to account for this would necessarily use the
same functions that we're trying to test, I've instead just made the
test program conditionally bypass the problematic cases if the current
date is either December 31 or January 1. This way we get maximum
testing during 363 days of the year, but don't get false failures on
Dec 31 and Jan 1.

Since there isn't a single libc API to get this value, this patch
supplies one which gets the value by grabbing current time, then
converting that into a struct tm with gmtime_r(), then back to a
time_t using mktime.

The returned value is the difference between UTC and localtime in
seconds. If localtime is ahead of UTC (east) the offset will be a
positive number, and if localtime is behind UTC (west) the offset will
be negative.

This function should be POSIX-compliant, and is threadsafe, but not
async signal safe. If it was ever necessary to know this value in a
child process, we could cache it with a one-time init function when
libvirtd starts, then just supply the cached value, but that
complexity isn't needed for current usage; that would also have the
problem that it might not be accurate after a local daylight savings
boundary.

(If it weren't for DST, we could simply replace this entire function
with "-timezone"; timezone contains the offset of the current timezone
(negated from what we want) but doesn't account for DST. And in spite
of being guaranteed by POSIX, it isn't available on older versions of
mingw.)
Signed-off-by: NEric Blake <eblake@redhat.com>

The source code base needs to be adapted as well. Some files
include virutil.h just for the string related functions (here,
the include is substituted to match the new file), some include
virutil.h without any need (here, the include is removed), and
some require both.

The libvirt coding standard is to use 'function(...args...)'
instead of 'function (...args...)'. A non-trivial number of
places did not follow this rule and are fixed in this patch.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

https://www.gnu.org/licenses/gpl-howto.html recommends that
the 'If not, see <url>.' phrase be a separate sentence.

* tests/securityselinuxhelper.c: Remove doubled line.
* tests/securityselinuxtest.c: Likewise.
* globally: s/;  If/.  If/

On OpenBSD, clock_gettime() exists in libc rather than librt, and
blindly linking with -lrt made the build fail.  Gnulib already
did the work for determining which libraries to use, so we should
reuse that work rather than doing it ourselves.

* bootstrap.conf (gnulib_modules): Pull in clock-time.
* configure.ac (RT_LIBS): Drop.
* src/Makefile.am (libvirt_util_la_LIBADD): Use gnulib variable
instead.
* src/util/virtime.c (includes): Simplify.

Per the FSF address could be changed from time to time, and GNU
recommends the following now: (http://www.gnu.org/licenses/gpl-howto.html)

  You should have received a copy of the GNU General Public License
  along with Foobar.  If not, see <http://www.gnu.org/licenses/>.

This patch removes the explicit FSF address, and uses above instead
(of course, with inserting 'Lesser' before 'General').

Except a bunch of files for security driver, all others are changed
automatically, the copyright for securify files are not complete,
that's why to do it manually:

  src/security/security_selinux.h
  src/security/security_driver.h
  src/security/security_selinux.c
  src/security/security_apparmor.h
  src/security/security_apparmor.c
  src/security/security_driver.c

The glibc time.h header has an undocumented __isleap macro
that we are using. Since it is undocumented & does not appear
on any other OS, stop using it and just define the macro in
libvirt code instead.

* src/util/virtime.c: Remove __isleap usage

The logging APIs need to be able to generate formatted timestamps
using only async signal safe functions. This rules out using
gmtime/localtime/malloc/gettimeday(!) and much more.

Introduce a new internal API which is async signal safe.

  virTimeMillisNowRaw replacement for gettimeofday. Uses clock_gettime
                      where available, otherwise falls back to the unsafe
                      gettimeofday

  virTimeFieldsNowRaw  replacements for gmtime(), convert a timestamp
  virTimeFieldsThenRaw into a broken out set of fields. No localtime()
                       replacement is provided, because converting to
                       local time is not practical with only async signal
                       safe APIs.

  virTimeStringNowRaw  replacements for strftime() which print a timestamp
  virTimeStringThenRaw into a string, using a pre-determined format, with
                       a fixed size buffer (VIR_TIME_STRING_BUFLEN)

For each of these there is also a version without the Raw postfix
which raises a full libvirt error. These versions are not async
signal safe

* src/Makefile.am, src/util/virtime.c, src/util/virtime.h: New files
* src/libvirt_private.syms: New APis
* configure.ac: Check for clock_gettime in -lrt
* tests/virtimetest.c, tests/Makefile.am: Test new APIs