Engine/Task/Ordered/OrderedTask: Clear taskpoint_start/taskpoint_finish when clearing a task

Fixes trac issue #2947.
MapWindowEvents: check if the projection is valid

Fixes assertion failure when the DrawThread is slow on startup.
OLCTriangle: better approximation of min and max distance

Reduces the number of needed iterations by 40% and memory
consumption by 30% in some cases.
Merge remote-tracking branch '_max/v6.6.x' into v6.6.x
android: Use xcsoarte app identifier only in AndroidManifest.xml

Use org.xcsoar everywhere else to reduce upstream diff
Merge branch 'v6.6.x'

Conflicts:
	build/android.mk