Add "abusefilter-bypass" userright as a hack for GlobalRename page moves

GlobalRename is having its page moves stopped by AbuseFilter rules
that shouldn't affect it at all. This is a temporary hack until
something like bug 67936 is fixed.

This is less evil than unsubscribing AbuseFilter from $wgHooks IMO.

Change-Id: I6b301fda119be167d3f092d86ba5914289045fab