Author: Tony Levi
MDL-49398 accesslib: Simplify role definition loading and cache
This change removes the complex and partial loading of role definition data for users.
It is replaced by keeping one system-wide definition for each role in MUC.
This is cheaper to regenerate as it avoids complex database queries (repeated LEFT JOIN to context).
Memory usage is kept low thanks to array CoW for each user access data.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=e705e69e7f787d18ead1a3cdf5d03ca08ad1f47b
http://github.com/moodle/moodle/commit/e705e69e7f787d18ead1a3cdf5d03ca08ad1f47b
+ 3.4 en [cachedef_roledefs,core_cache]