Reintroduce syslog facility/severity support

[sborsje]

Currently it's not possible to configure which syslog facility the syslog handler will log from. This means that all logs will be logged from the "kern" facility, since this is the default within the stdlib syslog package. This is confusing, because "kern" should be used for kernel logging only.

I noticed that syslog priority configuration used to be supported in this library, but it was removed in commit 54d74c8. Could you maybe reintroduce this? If not, it might be a good idea to pick a better default.

[inconshreveable]

Gah! This is my fault for not understanding how the syslog package works. When I wrote that, I mistakenly assumed that the caller didn't need to pass in the priority, because the log level would be set by each call. I missed the fact that priority is both the log level and the facility. You're right, we need to bring back the ability to set the syslog facility when creating the handler.

[raphael]

I'm hitting that same issue - is there more to it than reverting that commit?

[inconshreveable]

Reverted 54d74c8