NAME
valid_shadow - controls which objects can be shadowed
SYNOPSIS
int valid_shadow(object ob);
DESCRIPTION
When an object attempts to shadow `ob' (with the shadow() efun), valid_shadow
in the master object is called. One object parameter is passed, which is the
object that previous_object() is attempting to shadow. valid_shadow() should
return 0 if the shadow should not be permitted, in which case the shadow() call
will return 0 and fail. If valid_shadow() returns 1, the shadow is allowed.