Author: Sam Hemelryk
MDL-44711 navigation: improved expandable course calculation
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0f52f263cabccd0b4b163e222847d33ac65d8880
http://github.com/moodle/moodle/commit/0f52f263cabccd0b4b163e222847d33ac65d8880
+ 2.7 en [cachedef_navigation_expandcourse,core_cache]