fix cast warning in CTaskFileHelper.cpp
Fix 4.0 possible critical bug while drawing sectional airspaces, over 40 of them at the same time.
Added more check in lkassert.
	modified:   ../Header/LKAirspace.h
	modified:   Draw/Multimaps/RenderAirspaceTerrain.cpp
	modified:   LKAirspace.cpp
Merge branch 'fixWarning' of http://github.com/brunotl/LK8000
Fix compiler warning in Buttons
	modified:   Buttons.cpp