dumpcap: enable capture of pcapng from pipe

dumpcap: enable capture of pcapng from pipe

Reads pcapng blocks from a pipe.  Section header blocks are parsed for
endianess.  All other blocks only have the general block header parsed
for type and length, and then endianess converted if necessary.
Outputs all blocks using the original endianess format so none of the
other block types or options require parsing.

Change-Id: I2f4f0175013d8fc2cda42a63e7deacad537951e3
Bug: 11370
Reviewed-on: https://code.wireshark.org/review/24536
Petri-Dish: Dario Lombardo <lomato@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>