Support for pcap_create and associated functions

[ioguix]

Following the discussion on issue 1, here is the pull request with the patch discussed with some tests added.

Functions added:

• pcap_create(): create a non activated pcap handler
• pcap_set_buffer_size(): set the capture buffer size on a non activated pcap handler
• pcap_set_promisc(): set the posmiscious mode on a non activated pcap handler
• pcap_set_snaplen(): set the snaplen on a non activated pcap handler
• pcap_set_timeout(): set the capture timeout on a non activated pcap handler
• pcap_activate(): activate a pcap handler created with pcap_create()

PS: sorry for being so late to answer this :(