C network probing library

• demux the demuxer is a singleton that listens on a given interface (using sniffer) and calls listener functions.
• sniffer the sniffer calls a callback function for each UDP or ICMP packet arriving at a given interface.
• packet support functions for manipulating and storing packets.
• sender functions to send ICMP packets; allows fixing the forward and reverse flow identifiers.
• confirm a module that retransmits probes to address packets losses.