trie_insert

int trie_insert   ( trie_node_t ** rootRef, char word[ ] ){
        int i=0, index=0;
        int len;
        trie_node_t *tmp = *rootRef;
    len = strlen(word);
        for(i = 0;i<len;i++){
            word[i] = tolower(word[i]);
        }

    if (tmp == NULL) return EXIT_FAILURE;
    for (i=0;i<len;i++) {
            if (word[i] == '\0') index = 26;
            else if (word[i] >= 'a' || word[i] <= 'z') {
                index = charToInt(tolower(word[i]));
            }
            else return EXIT_FAILURE;

            if (!tmp->child[index]) tmp->child[index] = trie_new();

            tmp = tmp->child[index];
    }
    tmp->end= '\0';

    return 1;
}