ZeroMQ initial support (ZMTP/1.0 framing)

ZeroMQ initial support (ZMTP/1.0 framing)

This change adds support for ZMTP/1.0 (ZeroMQ Message Transport Protocol
1.0) framing in TCP packets, as defined in http://rfc.zeromq.org/spec:13
and implemented in zeromq library.

Since there is no assigned port number for ZeroMQ, the user is left
responsible for making only the related TCP packets captured and
enforcing ZMTP/1.0 decoding through the "-T zmtp1" option.

Each ZMTP/1.0 frame of a packet will produce a single additional line of
output. The "-v" flag will add up to 8 lines (128 bytes) worth of
hex+ASCII dump of the frame body, and "-vv" and higher will dump the
full frame body, however long.

Beware that this code handles neither IP fragmentation nor TCP
segmentation and will incorrectly decode segments not starting at a
frame boundary.

The included sample capture stands for a short ZeroMQ session between a
REQ/REP socket pair doing 3 anonymous 2-way exchanges. It was produced
using version 2.1.9 of zeromq library patched to fix its bug #293, so
that all MBZ bits of the flags field are set to 0.