iptrie: a retrieval tree optimized for ip addresses

functions:
    iptrie_init: initiate a iptrieroot_t structure
    iptrie_free: free a iptrieroot_t structure
    iptrie_alloc: internal memory allocation routine, uses chunks to save overhead
    iptrie_insert: insert a value into the iptrie, with a unique ip address
    iptrie_optimize: optimize an iptrie aka remove all items that have value NULL
    iptrie_search: find the value according to the ip address given
    iptrie_list: lists all ip addresses accordingly with their value
    iptrie_callback: enumerate all ip addresses and have the ability to remove certain values (setting them to NULL) returns amount of values changed