When the RTC preinit function fails, set the system clock to the time of
the last modification of the driftfile if it's in the future. This makes
the -s option somewhat useful on systems where RTC is not supported or
missing.
This is similar to the functionality implemented in the fake-hwclock
script.
If there are extra arguments on the chronyd command line, they will be
parsed as lines in a configuration file and the normal configuration file
will be ignored.
Add new DEBUG_LOG macro for debug messages. The messages are enabled
when compiled with --enable-debug and they are printed when the -d
option is used twice.
