CKLKUP    CKLKUP    CKLKUP    CKLKUP    CKLKUP    CKLKUP    CKLKUP    
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INTEGER FUNCTION CKLKUP (ITEM, LIST, NLIST)
Looks up an item in an integer list. If an item is found,
it returns the first position of the item in the list. If an
item is not found, this routine returns the value 0.

INPUT
ITEM    - Integer scalar; Item to look up in the list
LIST(*) - Integer array;  List of entries
NLIST   - Integer scalar; Number of entries in the list

RETURN
   integer position of the item in the list.