Add test for port access functions

Tests whether trace_get_source_port and trace_get_destination_port
work correctly.
Fix build bug with UNUSED in libwandio
Added trace_get_fragment_offset to API

New function performs all the bit-shifting, masking,
multiplying and (in the case of IPv6) header skipping necessary to
work out the fragment offset for a packet, in bytes.

Fixed trace_get_source_port and trace_get_destination_port so
that they do not try to lookup port numbers if the packet is
not the first fragment.

IPv6 fragment offsets probably need more testing.
Add new test for fragment offset function

Update test suite to build and run new port and fragment tests.
Return 0 for port numbers for ICMPv6

This brings the behaviour in line with that for IPv4 ICMP.
Merge branch 'getfragoff' into develop
Fix missing HAVE_VISIBILITY dependency

Thanks Richard S. for finding this one.
Add read/write support for xz (lzma) files.
Merge branch 'master' of https://github.com/isomer/libtrace into develop
Merge branch 'master' of https://github.com/isomer/libtrace into develop
Integrate lzma into libwandio properly

Update configure to detect lzma properly.
Add missing get_compression_type API function to wandio code.
Add code to detect if input file is LZMA.
Added help text to wandiocat.

Also changed indentation to match the rest of libwandio, as it
was annoying to work with otherwise :)
Merge remote branch 'origin/develop' into develop
Add missing fragtest trace to repo
Increment libwandio version number
Increment libtrace version number to 3.0.20
Increment version number to 3.0.20
Remove duplicate macros in libpacketdump

Ensure OSPF libpacketdump module won't segfault or print garbage
if a truncated OSPF header is passed into it.

Renamed 'len' field in OSPF header to 'ospf_len' to avoid
potential conflict with variables named len in libpacketdump
code.
Merge remote branch 'origin/develop' into develop
Added unit test for lzma autodetection