Norfolk Island's standard time (NFT) was on UTC+11:30 until 4 October
2015, when it was changed to UTC+11:00. So it's not suitable for 11.5
bad mapping replacement anymore.
It seems that there isn't any other location using such 11.5 timezone
so completely getting rid of it for conversions.
This patch replaces all homegrown timezone
stuff with standard PHP date/time code.
The main change is the introduction of core_date
class that returns normalised user and server
timezones. From now on nobody should be using
$CFG->timezone or $user->timezone directly!
Other new features and fixes:
* admins are prompted for timezone during install
* editing of other users is finally fixed
* timezones are displayed in user profile
* new $this->setTimezone() in phpunit
* time locale is now automatically reset in phpunit
* timezone is now automatically reset in phpunit
* phpunit has Australia/Perth as default timezone
