Author: Jake Dallimore
MDL-66147 core: add get_time_interval_string()
Returns a formatted string representation of the difference between two
timestamps, defaulting to 'Xd Xh Xm' format, but supporting custom
format strings containing any chars from:
https://www.php.net/manual/en/dateinterval.format.php.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=612b210d7692e46a821f6ac18d87ecba96ef2b51
http://github.com/moodle/moodle/commit/612b210d7692e46a821f6ac18d87ecba96ef2b51
+ 3.8 en [relativedatestimediffformat,core]