This patch adds asynchronous backup and restore functionality
to Moodle. This is an optional feature and is not enabled by
default. It can be enabled by site administrators.
Asynchronous backup and restores are actioned by the Moodle
adhoc task API. The progress of backup and restores is
displayedin the Moodle UI. Users can also be sent a message
when a backup or restore operation completes via the
Moodle messaging API.
When doing a backup or restore operation with the normal user interface,
if there is anything in the backup/restore log, it will now be displayed
at the end of the process below the Continue button.
If you have developer debugging enabled, it sets the display level to
LOG_DEBUG and there will always be content in the log. Otherwise, it
uses LOG_INFO which generally means the log is empty, and nothing
displays (no visible change for users).
Adds 'Preparing page display' progress bars for user interface pages
if they take a long time to display.
Also adds changes where other parts of the backup progress timed out on
long backups. After this change, and MDL-41838, it is finally possible on
my dev server to successfully back up the 'XL' test course.
