DF-11 SI/II Detection changes

Don't allow detection of DF-11 SI/II until we have received at least one
DF-11 for the aircraft with an SI/II of zero.

Previous versions would allow an ICAOAddr to be marked as valid if a
DF-11 was received where the crc was less than 80. This is required for
SI/II detection where the SI/II is overlaid on the crc field. However,
this also decreaces the security of the crc. It is possible for a
corrupt message to result in a crc value of between 1 and 79, and this
will lead to an invalid ICAOAddr being marked as received.

To try and prevent this, do not allow detection of DF-11 II/SI fields
until at least one DF-11 crc=0 has been received. Once this happens, we
ca be fairly sure that this aircraft really is within range, and so
II/SI detection can e used.
Bugfix in position decoding

If the aircraft lands or takes off, the Lat/Lon valid flags are cleared.
In the original code, this also resulted in any even/odd position
reports in the mm record being discarded  This meant that the code would
require an even and odd position after the change of flight status.

The code had been modified so that any position report in the mm record
is used even if there is a change of flight status. This means there
only needs to be an even or odd after a change of FS, rather than
requiring both even and odd. The result should be earlier decoding of
position.
Extra list decoding for DF-0 and DF-16

Extra list decoding for DF-0 and DF-16
Tidy up a few things
Change version number