* do not log an empty new line when writing to syslog
* allow operator to configure truncation on syslog

The go standard library implementation of log/syslog has been abandoned
and is no longer maintained. In our tests with syslog logging in
gorouter we noticed a significant performance penalty over file based
logging. However, with file based logging we frequently observe broken
logs because logrotate interferes with log reading / writing.

This commit inlines the relevant file from log/syslog and refactors the
implementation to be on-par with the file based logging.

Co-authored-by: Alexander Lais <[email protected]>