logger: add process --id=parent optional argument

When scripts send several messages they will be easier to group together
when parent process id is printed rather than id of the each logger
process.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
logger: make --stderr print remote server messages

Users wish to see the message should include also remote messages, not
only the one sent to locally via libc function.

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