Syslog fix for not Windows systems.
Made SyslogDestination abstract, created UnixSyslogDestination and WindowsSyslogDestination.
Typo fixes.
Added platform defines.
Made Init() pure virtual too.
Made InitLoggingFromFlags a wrapper around InitLogging(log_level, log_output).
Merge remote-tracking branch 'upstream/master'

Conflicts:
	common/base/Logging.cpp
Merge pull request #435 from sebokmarton/master

Syslog fix for not Windows systems.