vacation.php:
- check that $tActiveUntil >= today and $tActiveUntil >= $tActiveFrom
- update header comments
- display "vacation is active" notice also to admins
(based on a patch by J.Kruis @SF,
https://sourceforge.net/p/postfixadmin/patches/122/ )

*.lang:
- add 
  - pVacation_until_before_today
  - pVacation_until_before_from
  - reply_once_per_day
- change pUsersVacation_welcome_text to 'Auto response for %s is active!'
- remove "obsolete" marker from pUsersVacation_activefrom and
  pUsersVacation_activeuntil, they are still used

nl.lang:
- translation update by J.Kruis @SF
  https://sourceforge.net/p/postfixadmin/patches/122/



git-svn-id: svn://svn.code.sf.net/p/postfixadmin/code/trunk@1697 a1433add-5e2c-0410-b055-b7f2511e0802