Author: Tim Hunt
MDL-34399 questions: cache to help load question definitions.
At the moment, it takes several DB queries to load each question definition,
so this cache is potentially a big win.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=a560d636f4a8929ba21c38a40c145c861e831d07
http://github.com/moodle/moodle/commit/a560d636f4a8929ba21c38a40c145c861e831d07
+ 2.4 en [cachedef_questiondata,cache]