MDL-41754 (1) Progress tracking : moved from backup and restore to core
MDL-41754 (2) quiz statistics : using Sam's new progress classes
MDL-41754 (3) quiz statistics : need to escape core_php_time_limit

after MDL-42084 was merged into upstream, introducing
core_php_time_limit, this branch that moved a reference to
core_php_time_limit to a new namespace was broken.