only write stderr to syslog when using flag --syslog and --syslog-stderr

[kkeybbs]

New flag "--syslog-stderr" added.

As "--syslog" logs too many to syslog, with this new flag, logs to stderr will be logged to both stderr and syslog, to reduce log size in syslog, and stdout logs will not be logged to syslog.

[rfjakob]

Hi, what part of the logging is too much? Can you post an example?

[rfjakob]

Waiting for feedback, marked as draft for now