POSTFIX_CONF.txt:
- add note that active=1 needs to be changed to active='t' when using 
  PostgreSQL
  https://sourceforge.net/p/postfixadmin/discussion/676076/thread/016fe62e/
- move around note about concat() vs. PostgreSQL


git-svn-id: svn://svn.code.sf.net/p/postfixadmin/code@1682 a1433add-5e2c-0410-b055-b7f2511e0802