NAME
        AddHead -- insert node at the head of a list

   SYNOPSIS
        AddHead(list, node)
                A0    A1

        void AddHead(struct list *, struct node *)

   FUNCTION
        Add a node to the head of a doubly linked list. Assembly
        programmers may prefer to use the ADDHEAD macro from
        "exec/lists.i".

   WARNING
        This function does not arbitrate for access to the list.  The
        calling task must be the owner of the involved list.

   INPUTS
        list - a pointer to the target list header
        node - the node to insert at head

   SEE ALSO
        addtail(), enqueue(), insert(), remove(), remhead(), remtail()