Not directly related with cron, but detectez while monitoring it.

Petr has detected that on course deletion, records aren't deleted from the user_lastaccess table. Fixing includes:

• delete such records in the delete_course() function
• delete such records if necessary in reset_course()
• delete when one user auto unenrol from one course?
• as part of the upgrade, delete all records belonging to nonexistent courses.

Call this the ORPHAN_BY_COURSE_DELETE_PROBLEM.