fix drawing airspace pictogram thread conflict !
Normalize Code Format, no code change in this commit.
Add LKASSERT and prevent division by zero in LKAirspace
Fix allow multiple instances of LK to run at the same time in PC testbench mode.
To use an old version of LK, such as 4.0, run it before running this new .
fix  : overlays value like "Next Arrival Alt Diff" is not updated on multimap.
Fix drawrunway no more correctly drawing airfields at low resolutions.
Adjusted old version mixed with picto.
Drawing glidersite is still quite useless at low zoom levels on some resolutions.
Merge branch 'MMOverlay' of https://github.com/brunotl/LK8000