LMP: add -T override and fix version 1 test(s)

The Link Management Protocol version 1 sample capture added to the tests
directory in commit 212eef2 was produced using non-standard UDP port
49998. Later assignment of port 701 reflected in commit 960aee5 made it
impossible to decode the capture.

This change adds a -T override for LMP, uses it to replace the broken
test with two working tests and dismisses the custom test script,
lmp.sh.
adjust order of elements in ndo_printers[]

DLT_EN10MB, the most commonly seen datalink type, used to be the first
element of ndo_printers[], which lookup_ndo_printer() iterates over, but
commit 20ad836 made DLT_NFLOG the first. Move DLT_NFLOG to the last
position to make the function spend the same time processing the
previously recognized datalink types as before.
SCTP: remove an unused variable (compiler warning)
OpenFlow 1.0: enable decoding of nested frames

The packet that may be contained in an OFPT_PACKET_IN or OFPT_PACKET_OUT
OpenFlow message is a plain Ethernet frame. Make it possible to have
ether_print() process that frame, with a controlled verbosity level (see
a comment in print-openflow-1.0.c for details). Update an existing test
case to employ the new feature.
LMP: fix some minor output issues

Fix a typo and suppress trailing spaces/tabs in a few cases.
NFLOG: remove header dependency, add a test case

This change removes detection of linux/netfilter/nfnetlink_log.h, which
was only used to provide two constants. The constants are now defined in
print-nflog.c, making it possible to compile (and test) the NFLOG
decoder on all systems, not only Linux.

There is now a test case for the decoder, it was produced on a Linux
host with:

iptables -A INPUT -p udp --source 74.82.42.42 -j NFLOG --nflog-group 20
dig @74.82.42.42 ...
add support for pcap_setdirection() (GH#252)

Adds -P in|out|inout option, includes man page and command line help
updates.
simplify pcap_setdirection() detection

AC_CHECK_FUNCS() already defines HAVE_xxx symbol, there is no need to
do this explicitly.
add a test case for syslog over UDP

The new capture contains two datagrams produced by logger utility
(syslog default timestamp format) and two datagrams produced by rsyslog
(RFC3339 timestamp format). One of the rsyslog datagrams has priority
consisting of two figures and the other -- of one figure.
fix parsing of syslog priority (GH #264)

...the code

* first looks for '<' and advances to the next character,
* it looks for a number between 0 and 9 and advances to the next
  character, (it finds 7)
* it looks for '>' and advances to the next character,
* it looks for a number between 0 and 9 and advances to the next
  character, (it finds the '2' of '2010')

=> result: prio is 72 instead of 7.

The code that checks if the character is '>' should be outside the loop
that checks if the character is a number. The attached patch moves this
check.
syslog: refine the decoder

Switch to TCHECK2() and improve format checks further. Remove some
excess code, an unused #include, some trailing whitespace and a few
empty lines.
Rename README to README.md
README.md: Markdown formatting tweaks
refine tcpdump(1) manpage (GH #119)
README.md: Remove VCS header line; add title and Travis CI build badge
README.md: Fix typo: INSTALL => INSTALL.txt
Merge pull request #332 from msabramo/README_markdown

Convert README to Markdown (README.md) + typo fixes + formatting tweaks + Travis CI build badge
LMP: amend tests/.gitignore
justify declarations of struct tok arrays

Make sure all of them are declared const and most of them -- static.
Proper declaration of token arrays is a common review point for new code
that is based on existing decoders. Thus fix the issue at its root.
add support for experimental tcp fast open and parsing experimental options