Update cleanupSpam.php to hide its activity from RecentChanges

Update cleanupSpam.php to hide its activity from RecentChanges

Spam cleanup activities, mostly when it comes from automated processes
(the so called 'spambots') can involve a fair ammount of edits and log
actions to accomplish.

As such, to avoid flooding Special:RecentChanges, this script will now
set a bot flag on the script run so its edits and actions won't show
up in that special page.

To prepare this patch I had the help of Bartosz Dziewoński which I'd
also like to thank and I'll credit as co-author as well.

Bug: T176206
Co-Authored-By: Bartosz Dziewoński <matma.rex@gmail.com>
Change-Id: Ifde08056a7481b877b4b82699cc0a5ea3f962dd9