[TYPO3-core] RFC #12066: Code cleanup: Add some constants

[Sigfried Arnold]

-1 one from me.

* Should be replaced by coding guidelines for using predefined escape 
characters (\n, \r, \t) - see PHP documentation for more info. Using 
chr(10) is imho bad style anyways.
* Naming is a bit odd (for the "ONE_xx" stuff); it's already said that 
60*60 or 60*60*24 is common and very clear.

regards
Sigfried Arnold