Replace linux pcap stubs accidentally lost in beefa72e97b1b55e0d2e4b214e8c411b65e097a2

The tuntap stubs have moved to the tuntap package.
Merge pull request #35 from djs55/linux-pcap-stubs

Replace linux pcap stubs accidentally lost in beefa72e97b1b55e0d2e4b214e...