[ticket/12800] core.functions_display.display_user_activity.actives_after

Adding core.functions_display.display_user_activity.actives_after

PHPBB3-12800
[ticket/12800] Missing $phpbb_dispatcher as a global

PHPBB3-12800
[ticket/12800] removed superfulous tab character

PHPBB3-12800
[ticket/12880] Changed name change @since as requested

Changed name to core.display_user_activity_modify_actives as requested

Changed @since to 3.1.0-RC3 because RC2 is already out.

PHPBB3-12880
Merge remote-tracking branch 'brunoais/ticket/12800' into develop-ascraeus
Merge branch 'develop-ascraeus' into develop