Sets the snip's administrator. Only an administrator should call this method.
The default method sets the internal state of a snip to record its administrator. It will not modify this state if the snip is already owned by an administrator and the administrator has not blessed the transition. If the administrator state of a snip is not modified as expected during a sensitive call to this method by an instance of text% or pasteboard%, the internal state may be forcibly modified (if the new administrator was #f) or a surrogate snip may be created (if the snip was expected to receive a new administrator).
The snip's (new) editor is usually internally locked for reading when this method is called (see also Locks).