fix declaration of otv_print() and vxlan_print()
fix two printf format strings
fix two issues with PGM length handling

1. "TSDU Length" comes in network byte order on wire, add missing macro.

2. The (unused) justification of the number of bytes on wire wasn't
correct because one side of the comparison included header size and
another didn't (note the byte order as well). Besides that, the value of
TSDU Length was already output thus far. Don't justify the number of
bytes on wire and change the final printf() to make a use of it.
add a test case for native PGM

This commit adds a capture of a few PGM (IP protocol 113) packets
produced with version 2.2.0 of zeromq library built with PGM support
(using the "pgm://" protocol schema). Each of the three ODATA packets in
the capture contains a ZeroMQ datagram in the "Data" (application data)
field. There is a new test case covering the PGM part of the capture.
use existing PGM decoder for UDP-encapsulated PGM

The original PGM uses its own IP protocol number. "EPGM" or "PGM/UDP"
stands for UDP-encapsulated PGM, which has no assigned UDP port number
and can be decoded only by means of -T option, which now accepts "pgm"
protocol type for this purpose. There is also a sample capture of EPGM
now (similar to the one of native PGM, but produced using the "epgm://"
protocol schema) and a respective test case.
enable decoding of ZeroMQ inside of PGM and EPGM