[Twisted-Python] patch for t.p.logger.SyslogObserver (was #7549)

[Roberto Polli]

Hi Glyph|all,

I just noticed the t.p.logger is gone (or integrated). This made 
the patch for supporting logLevels in t.p.syslog straightforward: 

https://twistedmatrix.com/trac/attachment/ticket/7549/syslog-loglevels-7549.patch

There are plenty of tests and it worked nicely on my env,
allowing rsyslog to split my twistd app log in various files with different
priorities.

If you see some flaw in the tests just let me know... once I roll it 
for a while on my apps I'll put the ticket in review.

Sorry for the great delay :( 
Peace,
R.

-- 
Roberto Polli