* A trigger can define one or more variables. If any one of them is
* currently referenced by any other trigger, this function will
* determine that.
-
+ *
* Typically used to determine whether or not a trigger can be removed
* - if there are any references to a trigger's variables, it cannot.
*
* events. However, for convenience, users are allowed to directly
* specify an event field in an action, which will be automatically
* converted into a variable on their behalf.
-
+ *
* This function creates a field variable with the name var_name on
* the hist trigger currently being defined on the target event. If
* subsys_name and event_name are specified, this function simply