[TYPO3-v4] Harmonizing severity levels

[Xavier Perseguers]

Hi Francois,

> I've started working on the "devlog" extension again. One thing I meant
> to do was to harmonize the severity levels with those used in
> FlashMessages, but this is far from trivial as those levels don't
> correspond at all. See the devlog's bugtracker entry for an overview:
>
> http://forge.typo3.org/issues/10638
>
> I would quite like to have your opinion on the issue. Do you think it's
> worth the effort? What should be done exactly? It's of course possible
> to adjust all t3lib_div::devLog calls in the Core, but what about
> extensions?

I'd like to have common levels as in Log4j:

TRACE,
DEBUG,
INFO,
WARN,
ERROR and
FATAL

and of course we should have constants instead of meaningless values.

Xavier