Act as if it was always set.
The ChildSession::_multiView field will always be true, so factor it
out. Ditto for Document::_multiView.
The ClientSession::_haveEditLock will also be always true, so factor
it out. This means the ClientSession::isEditLocked() will always
return true, so factor it out, too.
ClientSession::markEditLock() always will always set _haveEditLock to
true (which it will be from the constructor already anyway) so it can
be removed.
ClientSession::setEditLock() does not need a parameter as the
parameter was actually only used for misleading logging. The msg
variable constructed in the function used isEditLocked(), not the
parameter.
We still generate and handle editlock messages. Not sure whether that
makes any sense, though.
