IPv6: refresh options decoding (GH #47 pt. 3)

Brian Haley points that mobility (sub-)options decoded in
print-ip6opts.c are specific to draft-ietf-mobileip-ipv6 only. RFC3775
(and respectively RFC6275) uses different encoding and parameter space,
which print-mobility.c already handles.

Remove deprecated code and update some related macros.
added RPL decode for DAO and DAOACK, refactor out option printer
added decoding of RPL DAO and DAOACK sub-options
Merge branch 'master' of git+ssh://bpf.tcpdump.org/tcpdump/master/git/tcpdump
added test case for a DAO-ACK with no options
make sure that DAOACK option printer gets accurate length, and does not indicate truncated spuriously
RPL: test data and fix for printing DAO messages
RPL: rename test case files to be more clear as to their purpose
Include rpl.h in the tarball.
struct newesp is required regardless of whether we have libcrypto or not.
Various fixes.

Get rid of zero-length arrays; not all compilers support them.

Get rid of __attribute__((packed)); not all compilers support it, so we
can't depend on it.

Use explicit constants for sizes, just in case some compilers pad
structures.

Add some length checks.

Make some ND_TTEST2 calls ND_TCHECK2 calls instead, so they report
truncation if they fail.

Constify some pointers.
add a decoder for Loopback/CTP

tcpdump used to print an empty line for a Loopback (CTP) packet, which
many Cisco switches send by default every 10 seconds. This commit adds
a decoder for the protocol and a test case, which uses the sample
capture from Wireshark wiki (configuration_test_protocol_aka_loop.pcap).
reset the counter after a -G rollover (GH #352)

when -G -C is used the filename counter continued. Changed the behaviour
so that when -G is rolled over to the next file the Cflag-counter is
reset to 0 so that the filenames will restart counting.
Improved output of -D
Added bittok2str().
fixup status_flags[]

Add guards to fix building against older libpcap versions (PCAP_IF_UP
and PCAP_IF_RUNNING belong to the latest libpcap only). Add a
terminating element to the array. Justify some indentation.
justify declaration of loopback_print()

This fixes a MSVC warning Gisle Vanem reports.
justify more function declarations
refine option parsing a bit

My wish is to put minimal code inside the getopt() switch. So I've added
a Dflag for option '-D' and a new function show_devices_and_exit().
Multi-byte fields are in network byte order; fetch them appropriately.