Function raxGenericInsert

Insert the element 's' of size 'len', setting as auxiliary data * the pointer 'data'. If the element is already present, the associated * data is updated (only if 'overwrite' is set to 1), and 0 is returned, * otherwise the element is inserted and 1 is returned. On out of memory the * function returns 0 as well but sets errno to ENOMEM, otherwise errno will * be set to 0. */