Include Vertical rate in aircraft structure
Set AOG_VALID for DF-17/18 metype 19
SBS Output Format changes

Bug fixes in the SBS output code as a result of an EMAIL from Liviu

Some software gets upset if null fields are output where the software is
expecting a valid value. This was being caused by DF0's outputting and
SBS MSG5. MSG5 needs Atert and SPI flags, which are derived from the FS
field. DF0 doesn't have an FS field, so cannot output a MSG5. Change so
that DF0 results in an SBS MSG7.

Also DF17/DF18 metypes 5 to 18 contain raw Lat/Lon data. However they
cannot be decoded into real Lat/Lon values unless both even and odd
parts are available Therefore, when we receive a DF17/DF18 we need to
check that we have successfully decoded the Lat/Lon before we attempt to
send an SBS MSG2 or MSG3. If we don't have a decoded Lat/Lon, send a
MSG7 instead.
UKUEHN : Various Improvements

Sorry Ulrich - I can't get Github to resolve the merge errors and
preserve your commit notes, so I'll add them here.
Improvements on bit error correction, doc update, preparation for
program installation/package build

Hi,
I committed some further improvements on the bit error correction code,
updated the readme, and implemented a way to install the program in the
linux file system hierarchy (allows for package building).

Regards,
Ulrich
Tidy up of UKUEHN's improvements

Resolves some merge conflicts that I couldn't find a way to fix during
the previous merge.

Remove a few Tabs that escaped in the edit/merge

Rename the fix_errors flag variable to nFix_crc since it now represents
the number of crc errors to attempt to fix.

Remove the aggressive variable since it's now part of nFix_crc

Only print phase correction statistics when phase correction is enabled.

Add an additional Modes.stat_ph_bit_fix[] to count the bits fixed during
phase correction
VK1ET : Numerous changes to Port handling

Changes based on ideas from John VK1ET. His commit notes are as follows
:

1. Change input socket handling to avoid unnecessary memmove (use
pointers instead)

2. Add ability to read and decode binary beast format TCP.

3. Change output socket handling same as sbs_output - only call output
handler if there is a current client connected use separate ports for
beast in and out - no need for --net-beast flag. Will input/output
format defined by socket connected to. avr raw, beast binary and sbs can
be handled simultaneously.

4. Some comments changes, filtering of ModeAC to json,.
Move declarations into a headed file

This is the start of breaking the main dump109.c file into smaller
modules to make it a bit more maintainable.

Move all the #define and structure declarations into dump1090.h
Merge pull request #9 from MalcolmRobb/master

Pulling in from MalcomRobb's master updates