set default values for fields on push

as described in the oepnflow 1.3.2 spec
update dump_flow_tables()
Merge pull request #72 from iHiroakiKawai/push_with_defaults

set default values for fields on push
fix warnings
pcap library capture support

In some cases SOCK_RAW does not capture vlan tag, and
generates a stripped packet. This happens on recent linux
which has PACKET_AUXDATA in <linux/if_packet.h>.
Compiling with -DWITH_PCAP -lpcap will create a libpcap
enabled version of trema switch.
Merge branches 'with_pcap' and 'with_pcap' of https://github.com/iHiroakiKawai/trema-edge into with_pcap