Fix bug 7715:

Fix bug 7715:
* Add two conditional functions date_default_timezone_get() and date_default_timezone_set()
  which are created if they are not available (PHP <5.1.0).
* Replace setenv( TZ= ) and getenv( TZ ) calls with date_default_timezone_get( TZ ) and
  date_default_timezone_set( TZ ).
* Remove some warning supression calls, they were suppressing an E_STRICT level error that
  is thrown in PHP >5.1.0, however the above changes stop that error from ever occurring
  in the first place.
* Alter comment in DefaultSettings.php to refer to this function rather than the old
  method of using setenv().
* Add item to RELEASE-NOTES bug fixes section and fix line width of one item.
Based on attachment 2577 by nekocue.