Replay: tear down threads before exitting

NKQ is a generated name - don't copy it across to output

Stop whinging about presence of NKF6 and friends; we know these generated names are not going to be present in modern logs

memcpy rather than strncpy within log_FMT

Correct strings vs optionally-terminated structure entries in sanity checks

Call AP_Param::load_all() to start the parameter saving thread.  AP_Compass' init() method now saves parameters (compass reordering), and because we're disarmed we will block until the parameter is pushed onto the to-save queue; if there's no thread popping off that list we block indefinitely.

Remove duplicate definitions of various singleton objects.

Replay: write out GPS message to output log

Useful for diagnosis, but also because we struggle to find a time base
without this and the pymavlink tools take forever to work

Replay: set COMPASS_DEV_ID and COMPASS_PRIO1_ID so EKF gets mag data

Replay: avoid use of system clock; use stopped-clock only

Replay: constraint to emitting output for single core only

We haven't initialised the GCS at all, so it's not a great idea to
update_receive() and the like.

Also don't compile in the stop_clock symbol to make it clear changes in
this method won't affect vehicles