logger: allow use of --id=ppid when logging locally

logger: allow use of --id=ppid when logging locally

There is no obvious way to make syslog(3) to print both pid or ppid, so
duplicate the libc syslog() to logger.  Making the ppid printing work
using unix socket has side effect of local becoming capable to use both
rfc format output, which is hopefully seen as good thing.  The
syslog_local() is format wise one-to-one copy with glibc syslog(3)
format.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>