examples/ip_pipeline: add pcap file source

examples/ip_pipeline: add pcap file source

This patch add PCAP file support to ip_pipeline. Input port type SOURCE
now supports loading specific PCAP file and sends the packets in it to
pipeline instance. The packets are then released by SINK output port. This
feature can be applied by specifying parameters in configuration file as
shown below;

[PIPELINE1]
type = PASS-THROUGH
core = 1
pktq_in = SOURCE0 SOURCE1
pktq_out = SINK0 SINK1
pcap_file_rd = /path/to/eth1.PCAP /path/to/eth2.PCAP
pcap_bytes_rd_per_pkt = 0 64

The configuration section "pcap_file_rd" contains full path and name of
the PCAP file to be loaded. If multiple SOURCEs exists, each shall have
its own PCAP file path listed in this section, separated by spaces.
Multiple SOURCE ports may share same PCAP file to be copied.

The configuration section "pcap_bytes_rd_per_pkt" contains integer value
and indicates the maximum number of bytes to be copied from each packet
in the PCAP file. If this value is "0", all packets in the file will be
copied fully; if the packet size is smaller than the assigned value, the
entire packet is copied. Same as "pcap_file_rd", every SOURCE shall have
its own maximum copy byte number.

To enable PCAP support to IP pipeline, the compiler option
CONFIG_RTE_PORT_PCAP must be set to 'y'. It is possible to disable PCAP
support by removing "pcap_file_rd" and "pcap_bytes_rd_per_pkt" lines
from the configuration file.

Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>