Update to 2.7.2(security update)

Upstream changes:
Highlights
MDL-45780 - Atto now working with form change checker and quiz autosave
MDL-46748 - Mathjax address that changed, that caused Atto to fail to load, has been updated in Moodle
MDL-35984 - Gradebook Sum of grades shows correct total if items are hidden
Functional changes
MDL-45724 - Warning given when the same memcached instance is used for both sessions and MUC
MDL-46681 - For Multiple choices questions in the quiz / question bank, the options "Clear incorrect responses" and "Show the number of correct responses" did not make sense for "One answer only" questions. It is now impossible to select that combination of options on the form.
Security issues
MSA-14-0033 URL parameter injection in CAS authentication
MSA-14-0034 Identity information revealed early in Q&A forum
Fixes and improvements
MDL-37509 - Description of assignment hidden in calendar if "always show description" = NO
MDL-46545 - Weekly stats now working again
MDL-46589 - Automatic emails now sent after users import from CSV
MDL-43197 - Parent role only sees course total and no longer individual grades
MDL-46236 - Start New Attempt option is now followed if SCORM is set to appear in a popup

Approved by:	wiz@
Updated www/moodle to 2.7.2