Add unit test for bp_activity_delete_by_item_id()

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8528 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Don't use extract() in bp_activity_delete_by_item_id().

See #5698

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8529 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Improved formatting for docblocks in bp-activity-functions.php

See #5022

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8530 cdf35c40-ae34-48e0-9cc9-0c9da1808c22